I think with the loss of Rachael they’ll bring in female villains. I also think the horrible Catwoman movie is still too recent for her to come back, so I am putting my bet on either Talia or Poison Ivy and Harley Quinn. But I think the return of the League under Talia would rock. 
No one remembers the Catwoman movie. I think Selina Kyle would be a good villain to “Nolanize.” Make her a skilled thief with a background as a dominatrix. Explore her past in a few flashbacks. (She shouldn’t be a mysterious force of nature like the Joker.) Give her good motivation and put her right on the line between good and evil, another tortured soul in Nolan’s bat-verse.
You have to remember that if they make a 3rd movie its not going to come out next year. I think when it does enough time will have passed and catwoman won’t have the baggage she does now. She would fit in easily in the realistic view of these movies, she’s just a very skilled cat burglar after all.
I think a third movie would be great with her as the main antagonist alongside some obscure villain like Deadshot or even Clayface (whom, I think, would be possible to adapt to the movies).
What about The Penguin? Having never read the comics, why isn’t he viable?
He could be, if they did it right. Dump “The Penguin” as a nom de crime…except maybe as a pejorative used by his low-level henchmen behind his back. Introduce him as Oswald Cobblepot, a crime boss or former crime boss-turned-“fixer”, or go whole-hog into the Iceberg Lounge era as a retired criminal who runs a nightclub for the criminal underworld and occasionally sells information to Batman.
Have him dress formally at all times (maybe make it an OCD thing), but cut out the deformities of the DeVito version and the campy over-the-top manner and gadget umbrellas of the Burgess Meredith version.
I vote for King Tut. Who wouldn’t want to spend two and a half terrifying hours to find out how he gets konked on the head?
False Face. Master of disguise. He was kinda creepy in the old TV show. Or Azrael as a particularly obsessed "copybat, maybe a cop. That would set them against Batman.
From the realms of “I’ll believe it when I see it”: Alleged Casting wish list for Penguin & the Riddler.
Honestly, I have more trust in Nolan than to cast Depp and Hoffman. He chose Heath Ledger as The Joker for crying out loud, nobody would have expected that initially. Plus Aaron Eckhart as Harvey Dent was another genius casting role.
I don’t doubt that Hoffman would make a good Penguin and Depp would make a good Riddler, but it just doesn’t strike me as the direction Nolan would go for casting.
Hoffman would do a great job of The Penguin if he played him like Freddie Miles in The Talented Mr. Ripley. Snide, sarcastic, and pretentious, but with a dapper sense of style.
Not a fan of Depp, and wouldn’t want to see him as Riddler.
I think for new villains they should just say, to hell with it, and bring in characters from completely different media. Not just different comic books but whole different universes.
Batman vs. Anton Chigurh.
Batman vs. Sephiroth.
Batman vs. Revolver Ocelot.
Batman vs. Windom Earle from Twin Peaks.
Fuck it, why not?
Harvey’s not dead, but they covered it up to save the White Knight of Gotham icon. Bruce Wayne spent a fortune on physiological treatment and plastic surgery treatment for Harvey, to “cure” him. Gotham is beset by one or more baddies (Catwoman, Riddler, Penguin, whoever(probably not Catwoman, there is too much potential there WRT a relationship with Bruce to waste her)), and Batman’s effectiveness is diminished because he is now working outside the law. Harvey reappears and captures the criminal du jeur, catapulting him to iconic status, a shoo in for governor or maybe more, but he’s the Harvey from The Dark Knight Returns, and Batman, originally deliriously happy that Harvey has been redeemed, starts to notice the darker side of what he has created, Harvey is not all he seems. Chaos ensues, Harvey’s dark plan is realized, and Batman is forced to recognize the ashes that his dreams of redemption for Harvey have become. During the final epic fight, somehow Harvey becomes scarred over his entire face, and the movie ends with him screaming to Batman “Look at me! FUCKING LOOK AT ME! You succeeded! At least now I match!” to which Batman replies “I see a mirror Harvey. A mirror”.
Yes this is entirely the plot of The Dark Knight Returns Book 2, I’m not claiming any special insight for coming up with it, but it just FITS. Perfectly.
Oh and BTW, if Heath Ledger hadn’t died I’d be saying something different, but since he did, IMHO this would be the strongest Batman III movie possible.
How about Two-Face Two? Character biography, for those who don’t know it. Handsome actor Paul Sloane was making a movie about Harvey Dent. An act of sabotage by a rival actor caused him to suffer similar injuries to Harvey. He then began copying the same types of crime as the original. Maybe the rival actor could be Basil Karlo, the original Clayface, who was not a shapeshifting monster, but a an actor with an extraordinary gift for makeup and disguise.
It would be pretty tough to top Dark Night. I mean is Nolan going to start bustin’ out Mr Freeze?
And are they going to introduce Robin? I never liked Robin anyway. Here’s this dark menacing distubed guy draging some kid in a red suit around with him? Lame.
I’m going to go with Catwoman. Newly single Bruce Wayne falls in love with some girl who is a master criminal by night and hilarity ensues.
Also, does anyone else think of Patrick Bateman when they see Christian Bale playing Bruce Wayne?
See, now I’m imagining Batman lurking about Gotham City with a nail gun. This isn’t good…
and some really nice business cards
I think she should be plastic surgery addict who thinks she looks like a cat. That would be awesome.
Sounds like a great Venture Brothers episode, but a lousy Batman movie.
The casting would be easy.
Do we really need to give Jocelyn Wildenstein any more attention?
Isn’t catwoman just a catburgler? Seems that after defeating a demented terrorist’s attempts to blow up hundreds of people, uber-powerful mob families , and a team of ninja’s planning to nuke a city, having Batman go after someone whose worst crime is stealing some paintings and jewelry is going to be a bit of an anti-climactic third act.