SniperMacFox said:
How about we look at just the facts.
We know that this film won't be containing Joker, Two-Face, Riddler or Penguin and through them, I doubt it would contain Harley Quinn either... At a random stab, I'm going for the one word theme to be something like "trust" or "honesty" as a possibility, as then it could also include the introduction of Robin.
Word of God says there's no Robin either, so add him to the list. And Ra'as Al Ghul is dead, obviously, so it can't be him either.
Scarecrow and Mr Zsasz could feature, but since they've already been in it with quite minor roles, I doubt they'll be the main villains. Mr Freeze got a definite "no" a few months back.
We can safely write off anyone with superpowers too exotic, or gimmicks too camp - Killer Croc, Clayface, Manbat, The Mad Hatter, Maxie Zeus or The Ventriloquist.
The only viable candidates in my mind are one of the following: Poison Ivy, Catwoman, Hush, Bane, Talia Al Ghul or Black Mask.
Poison Ivy is usually depicted with actual superpowers, which obviously wouldn't work in the film, but it's not a stretch to see her reimagined as a conventional eco-terrorist. I doubt we'll see this though, ecology as a theme has been entirely absent from the rest of the series, and it'd be weird to have it materialise for the first time in this one. You can't even do a "destroying Gotham for the greater good" thing, cos that's already been done in Begins.
Catwoman or Talia Al Ghul seem more likely. Talia would be interesting exactly - having a connection to the League would really help Batman return to his roots, a theme that was explored extensively in Begins but more or less ignored in Dark Knight. And a love triangle between her, Bruce and Bruce's memory of Rachel is exactly the kind of quirky spin on a conventional plot line you would expect Nolan to do.
I doubt it'll be Bane, Hush or Black Mask for the following reason - they have no recognition beyond the franchise's fanbase. So what would be the point? I'm sure Nolan would much rather create his own characters to fit the story he has in mind than use somebody else's. The only reason to use existing characters is if they're already popularly associated with the Batman mythos, and I don't think any of these characters are.
Which brings me to a final possibility - maybe there isn't an established villain in the film. Maybe Nolan created one himself, or maybe there is no villain, period (the conflict between Batman and the police set up at the end of the Dark Knight could easily sustain a movie on its own). Can anyone point me to a quote from Nolan himself establishing that there definitely will be a VILLAIN from the comic books in this movie?