The Dark Knight was inspired by a few graphic novels, particularly The Long Halloween, The Man Who Laughs, and The Killing Joke. The more I read about this film, the more I’m pretty sure that this will be inspired by Knightfall, at least in part–or at least that’s what I hope.
In Knightfall, Bane (played by Tom Hardy in this film) is a genius who has enhanced his strength using a super-steroid serum called Venom. He proceeds to drive Gotham into chaos by wearing Batman completely down and eventually breaking his back. He overwhelms Batman by blowing open Arkham Asylum, freeing all of the insane super criminals, keeping the Dark Knight up for days on end. I think that, in light of the way The Dark Knight ended, this is a perfect direction for the film trilogy to go, ending with Batman’s redemption.
Obviously, this won’t be a straightforward adaptation, but it’s an interesting place to start.
Here are a couple of viral videos which were released that seem to confirm my idea, as well as a link to picture of Batman and Bane fighting.