Since even the Iron Islanders have heard of her, I think it’s general knowledge in Westeros.
The death of Tommen would cause a free-for-all, even worse than what’s already happened. As a practical matter, the throne will go to whoever can seize and hold it.
Pycelle, Cersei, and Littlefinger at the least. I would imagine all the major houses with any sort of informants know. Dany conquered three large city-states. She’s no secret.
With no better options, someone like Gendry could gain support, especially with a powerful backer. If everyone is desperate for leadership and stability, they might flock to the first claimant with any semblance of a claim.
Basically that’s how Henry VII managed to put an end to the Wars of the Roses - which were Martin’s model for the War of the Five Kings.
Well, that combined with defeating and killing Richard III in battle and then marrying the daughter of Edward IV, effectively uniting the Lancaster and York houses.
(Should Gendry therefore marry Dani?)
My main point was that Henry’s own claim was very tenuous (from a woman, and by illegitimate descent). Any claim can be made to stand up if it’s backed by a victorious army.
Gendry wouldn’t have to marry Dany, just someone with a strong army behind her. Given her past history, my bet would be Margaery. And then Gendry would promptly die. 
There’s no scenario when Tommen dies and Margaery doesn’t announce her pregnancy at the funeral and claim the regency on behalf of her unborn child. As Queen Regent she’d have access to the blondest bodyguards House Tyrell can supply to protect her in her delicate condition.
Yeah, the discussion about who has the most legitimate claim to the Iron Throne should Tommen die without a son to inherit is purely academic. Remember what Varys said when he told Ned the story in season 1: Power resides where men believe it resides. Robert’s claim to the throne was paper-thin, but his warhammer still dripping with Rhaegar’s blood and the massive army standing right behind him made compelling arguments in his favor.
Who has the power to take and hold the Iron Throne? That’s the only important question, it seems to me. As far as we know, the largest armies belong to House Tyrell of Highgarden and House Arryn of the Vale. If Tommen dies and Margaery is with child, the Tyrells would be well-placed to consolidate their hold on power while they waited to see if it was a boy – and substituting a boy for a girl if necessary is something I wouldn’t put past Margaery and the Queen of Thorns.
But I could see Littlefinger manipulating the situation to have Sansa declared either Wardeness of the North if not outright Queen in the North, and then marry her to her cousin Robin, putting the combined might of the North and the Vale behind them, and then put Robin on the Iron Throne on whatever pretext he needed to dredge up. Sansa produces at least one heir, then Robin goes through the Moon Door to join his creepy mother, and Littlefinger gets the daughter of the woman he once loved and all the power that goes with that.
I don’t know exactly how it could come together, but I trust Littlefinger to work out the details.
That could have been his plan at one point, but even if Sansa fell into his clutches again she’d never go along with that.
Now if Tommen dies, marrying Robin to Margaerys would ally the families with the two largest armies…
That’s… a lot more straightforward than I thought :smack:. Thanks ! 
Nope, that’s totally justified. Given the circumstances, a Valyrian steel sword has nothing to do hanging from a wall. What I noticed, on the other hand, is that Jon brought Mormont’s sword with him instead of leaving it at Castle Black, as he should have.
Mormont gave it to Jon personally, not to the Watch. Jon was justified in taking it. While he assumed Jon would continue to be part of the Watch, there was no one else who had a right to use it.
I’m with Colibri. It’s Jon’s sword, something I gather is a very personal thing. No way he should leave it behind.
Besides, if he thought the White Walkers were going to come knocking while he was away, he wouldn’t have left the Wall in the first place to go gallivanting around the North.
Mormont himself even had the pommel replaced with a Wolf, for Jon. Definitely passed personally from Jeor to Jon, after centuries in the Mormont family. Not the Watch’s sword.
It would be sure be quite an adjustment for Margaery to have to go from being married to an easily manipulated pubescent twerp who’s mother hates her to being married to an easily manipulated pubescent twerp who’s mother is dead.
A boy would obviously be preferable, but not essential since Tommen wouldn’t have any surviving brothers or nephews and both of his paternal uncles died childless.
History buffs, has anything similar ever happened in real life?
I doubt this is what they were going for but Sam stealing the sword and heading back up north would have been a great way to get his father–the best surviving general in Westeros–involved with the real war.
Yes, of course; history covers a very long time. Most famously this was the case with Alexander IV of Macedon, who was born two months after the death of his father, Alexander the Great.
That’s not quite what was meant I think. The idea is that Margaery would annouce “Well that’s horrible my husband died, but just before he got killed he knocked me up you guys !” to seize the moment, *then *find some Lannister stooge to knock boots with and hopefully get pregnant with.
And then the Queen of Thorns does her thing again on the lusty lad, presumably.
I’m not sure I know of any heir who was born 9-10 months after the previous king keeled over. That’s quite a long time for a kingdom to be rudderless (and quite a short time for a queen to have a regrettable accident…). The closest I can think of is John Ist the Posthumous, the son of Louis X the Quarreler ; who was born some 5 months after his dad died during a hunt. Incidentally the baby lived only 5 days and there’s quite a bit of suspicion that he was poisoned, most likely during his baptism.
Yeah, but in Littlefinger she’ll have a father-in-law who’s a lot smarter and thus more dangerous than Cersei.