Leaks:
>The 'cataclysmic event' is a massive bomb. Airburst tactical nuke to be exact. This is an action carried out under orders from the US government to deal with the Indian Hill (yes, 'the freaks' are coming back, Man-Bat among them), League of Assassins and Clown Cult madness which has started to spread to the mainland (very Dark Knight Returns), what follows is in essence total blackout, Gotham isolated, and Arkham City battlelines being drawn with what's left of the ruins being claimed by all factions. Ra's sees this as Gotham's chance to be reborn as it's practically destroyed.
>Jongleur and the Jester aren't the same character. Jongleur was in fact seen in the latest trailer alongside the Jester. The Jester is Ecco, and you can probably guess what Ecco's real name is revealed to be. She wasn't just Jeremiah's physical bodyguard, but also his psychological crutch.
>Jeremiah is the Joker, and he will be called that, but not in so much of a titular sense. "Alright mate, got ourselves some kind of joker here now, have we?"
>Jerome is back, but he's still dead. He continues to haunt Jeremiah and push him to become the 'new' Joker. The gas brings up repressed guilt from lying about Jerome as a child, makes him hallucinate Jerome tormenting him, he becomes more and more unstable, convinced that Jerome is in fact alive and coming for him. This is reinforced by plans Jerome made before his death where he arranged for his body to be removed from its coffin, and he recorded several videos to be aired following Cult attacks, intended to make it look as if he survived and is still on the loose. This is all responsible for giving Jeremiah the Joker's classic psychosis. (This is what's meant by the synopsis of a friend of Bruce's becoming paranoid and reckless.)
