Well, we could always say “screw genetics” and go with ideas like preformation. As it was put by Ted Chiang in “Seventy Two Letters”
I won’t give any more because it could give away part of the plot.
From HBP:
"Automatically, without really thinking about what he was doing, Harry pulled out the fragment of parchment, opened it, and read by the light of the many wands that had now been lit behind him:
*To the Dark Lord
I now I will be dead long before you read this but I want you to know that it was I who discovered your secret. I have stolen the real Horcrux and intend to destroy it as soon as I can.
I face death in the hope that when you meet your match,
you will be mortal once more.
R.A.B.*"
I think this means the locket can safely be written off, whoever R.A.B. turns out to be.
So that means we have left Nagini, Voldemort, the cup, and a relic of Gryffindor or Ravenclaw…
I like to think as well, that Regulus succeeded in destroying the locket horcrux, but Rowling leaves this unclear (at least, Harry ends in the book believing that there are four horcruxes left). On reflection, I think Regulus did succeed in hiding, but not destroying, the locket.
Apos mentioned something I think is going to be very signifigant in the final Potter novel. When Harry comes back from his duel with He Who Must…you know in GoF, he mentions to Dumbledore how Voldemort used his blood to resurrect himself. IIRC, Dumbledore asks him twice, just to be sure, then gets very, very pleased about that fact. Some part of the ending will have to hinge on the fact that Harry & HWMNBN are sharing blood, I’m just notoriously bad at guessing HP events, so I’m not venturing a guess.
Also: House Elf revolution in book 7. It has to happen.
Are you American? 
From what I have read on the net, it seems to be mostly Americans who have a problem with a slave-owning aristocracy as the good guys in a children’s story. I really hope it doesn’t happen because for me, the ambivalent wizard society was one of the strongest aspects of the series.
I am indeed. An American, I mean. And, you know, beyond that whole, good-guys-being-slave-owning-aristocrats thing, we know that the elfs are probably quite powerful (the end of book 2, with Dobby whooping up on Draco, as well as other examples I once had in my noggin but can not remember between work assignments) and, I think, by the end of book 7, most magical creatures will have to take one side or another. I’m hoping the elfs rise up, fight for good, and remain free. The wizard society can still be ambivalent, but the slaves would just revolt. Doesn’t mean the wizards have to be excited about it. They’d have to realize the elfs are a powerful ally though.
“Elves” or “elfs”?
In that vein, there’s a line in HBP where Dumbledore says that Harry’s blood is worth more than Dumbledore’s.
Wasn’t it Lucius?
Yes, it was Lucius. Dobby prevents him from hurting Harry after he reveals the sock deception. In the movie version it sounds to me like Lucius was about to use Avada Kedavra on Harry. I don’t recall if the book mentions the spell he starts to cast, been a number of years since I read it.
Total brainfart on my part—it was certainly Lucius. And I concur that he was about to use AK in the movie, which I also don’t remember from the novel, but could’ve been in there—yet, I doubt that Lucius would’ve dared use AK outside of Dumbledore’s office. (tangent: Lucius Malfoy was PERFECTLY cast in those movies. Just brilliant)
In the book, he just got as far as reaching for his wand, IIRC. In any event, he never uttered a single syllable. I was struck by his vocalization in the movie.
Actually, this could have been foreshadowed by the earlier mentions of the Goblin Wars.
That would be de-horcrucify, I think.
Dumbledore knows that Voldemort and Harry are tightly connected. He also knows, and it is proven in OotP, that Voldy finds love unbearable. Now that voldy has Harry’s blood flowing in his veins, Harry has an in. I don’t doubt Harry will find a way to exploit the connection to hurt and or destroy Voldemort.
Also because everybody always gives him books as a Christmas present, when he really needs some good pairs of socks more.
With as rare as the spell is to make Horcuces, a spell specifically for unmaking them would have to be rarer still. And Dumbledore isn’t even sure what the ring is, at the time that he renders it Perfectly Safe: He only gets confirmation about the Horcruces when Harry brings him Slugworth’s memory. So I’m going to guess that the spell used is more widely-known and of general use, perhaps some sort of Potterverse variant of Dispell Evil. Which still leaves the formidable task of finding out just what spell it is, and how to use it, but I think that puts us where it’s at least plausible that Harry et al. (especially Hermione) could find out.
It’s also likely that Voldemort himself knows the spell (since, after all, he’s the only person we know of who knows the Horcrux spell itself). He probably wouldn’t think Harry would be willing to make the necessary sacrifice (his life, his magic, or whatever), since the concept of altruism is so foreign to Voldemort, so he may even tell Harry himself during the final confrontation, to taunt him.
Not everybody gives him books; some people seem to think that a bottle of poisoned wine is a fine gift to commemorate the Birth of our Saviour.
You know, Jesus being a wizard would explain a lot.
I’m going to comment in scattershot fashion on some of the items I’ve seen in the thread. These are my guesses and don’t sue me when they are proven wrong after book seven.
Snape/Lily:
Snape was in love with Lily Potter, one of the reasons he hates James Potter so much. Snape also became a Voldemort follower / Death Eater. Snape, outside the room of the Hog’s Head where Trelawney is applying for a job at Hogwarts, hears part of the prophecy concerning Voldemort and some child born at the end of July. He rushes over to Voldemort with the news. Voldemort decides it’s the Potter boy or the Longbottom boy and that he must kill them both. Snape learns that Voldemort has killed Lily Potter, or is planning to kill Lily Potter, and is so consumed by rage (or grief) that he turns against Voldemort and goes to Dumbledore to betray he-who-must-not-be-named. Dumbledore has Snape make an unbreakable vow to protect Harry Potter’s life. (Which is why Snape saves Harry Potter in the Quidditch Match in Philosopher’s Stone, and why Dumbledore trusts Snape.)
Malodorous said “But Dumbledore trusted Snape as a spy during Voldemort’s first rise, before Lily was killed” - cite? We know that Dumbledore vouches for Snape during the trial of Karkaroff, as seen in the pensieve in Goblet of Fire, but Karkaroff’s trial happens after the fall of Voldemort. In any case, Snape could have turned against Voldemort because he (Snape) knew the Dark Lord was hoping to find the Potters and probably kill them to get to Harry.
Missing Horcruxes - like Chronos said, the missing locket / horcrux taken by a mysterious R.A.B. must be the golden locket found during the house cleaning of the Black house at the beginning of Order of the Phoenix. J.K. Rowling has pretty much admitted in an interview that R.A.B. was Regulus A. Black.
Ollivander and/or Florian Fortescue joining Voldemort? I think Ollivander might have (in their first meeting Harry Potter doesn’t particulary care for Ollivander, though, as Sirius Black reminds us, the world is not divided into good people and Death Eaters), but Florian Fortescue definitely not - he was a good friend to Harry and gave him tons of free ice cream. Harry’s enemies are not always death eaters, but people Harry likes have not (so far) turned out to be Death Eaters. Mad-Eye Moody in Goblet of Fire doesn’t count; Harry only liked the Death Eater impersonating Mad-Eye Moody because the Death Eater did a great job impersonating the real Mad-Eye.
Socks have been mentioned repeatedly in the Potterverse. Harry gets old pairs of socks from his uncle, Dobby gets a dirty sock of Harry’s to gain his freedom, Dumbledore claims to wish for socks, etc. But I think this is only because J.K. Rowling thinks socks are funny.
Did Lily Potter make the potion that protected the (missing) horcrux in the cave from Half-Blood Prince? Highly dubious. I think it more probable that Voldemort himself made the potion - he’s a master wizard after all. I doubt that the identity of the maker of that portion is significant.
The ending of Harry’s adventure - I like the idea that Harry will have to give up magic to conquer Voldemort. Meaning I think it would be a good ending, not that I would want Harry to have to go through that. I’ve seen someone in the thread saying how Ron might have to die in the final struggle. A comment that J.K. Rowling once made in an interview struck me; she found it surprising that many are worried about Ron Weasley getting killed, but no one seems to be apprehensive about the possibility of Hermione dying.
Every time I hear this theory it seems more and more terrible. It sounds like something cobbled together by shippers not because there’s any evidence of it, but because shippers are the kind of people that like to (figuratively) draw up two lists of characters and connect each character with another character. Because apparently in a work of fiction everybody must have feelings for one other character.
The entire basis for this supposition appears to be the scene in the pensieve, when Lily tells James and Sirius to leave Snape alone when they are bullying him. It takes a good deal of imagination to extrapolate “stop bullying that guy” to “me and him have a love thing.” It does not make sense.
Further, it makes even less sense to use it as the reason for Snape’s loyalty to (assumed) Dumbledore. Do you really think Dumbledore would be dumb enough to trust a defector on the basis of a teenage crush? Isn’t it entirely possible that Snape’s turning away from Voldemort is not some Harlequin-esque romantic gesture but simply because he’s an asshole who isn’t evil? Isn’t it possible that Dumbledore was simply a good enough character judge that he could recognize that in Snape?
Similarly, Snape’s hatred for Harry does not need to come from some grand emotional event. A lot of the time hatred is just irrational. Snape hated James, Harry reminds Snape of James, and that, coupled with Harry’s undeserved fame causes Snape’s hatred.
I know it’s grand and exciting to think that every single piece of character development must come from a Grand Life-Changing Event, but in real life, that’s not the way it usually works, and I think Rowling is smart enough to recognize that.
Also, if Dumbledore’s sock fascination and desire to remain on the Chocolate Frog cards are vital plot points rather than simply characterization, how does everyone think Dumbledore’s love of ten pin bowling will contribute to the downfall of Voldemort?
Finally, that Black family tree has some interesting stuff in it: Rysto’s link shows Sirius’ grandfather had a sister who married a Charlus Potter - that surname seems far too important for Rowling to have chosen it at random. Looks like Harry’s grandmother or great-grandmother was the sister of Sirius’s grandfather. Which means, once you take into account the presence of the Malfoys and the Weasleys on the tree, Harry is distantly related to Draco, Ron and… Ginny :eek:.
It’s not like they’re cousins or anything, true, but still!
I doubt any of that will figure into the plot though.