Although the studio and Christopher Nolan have been playing their cards very close to their chest of "Batman 3" Empire magazine have been able to confirm with the man himself that he's currently working on the sequel to "The Dark Knight".
He told Empire "It’s becoming inevitable, I’ll put it that way…I feel myself falling into it, I guess. And getting it all figured out and I’m pretty excited about what we’re doing so… If I haven’t announced it, I think that people probably all know at this point that I’m doing it."
And by that apparently we can presume that he means he will be directing the movies. He added "I think you can at this point, yes."
In the report they also confirm that he is working on a Jonathan Nolan script for the film. According to IMDB all main cast will return for the sequel with Joseph Gordon-Levitt cast in the role of The Riddler. The movie is due to be released in 2012.