In an interview with the LA Times, Christopher Nolan said the next Batman movie will be titled "The Dark Knight Rises" and the Riddler won't be the villain in the film. Other than those two snippets of information, Nolan played everything pretty close to the vest--as he usually does.
But, we do know Nolan recruited Tom Hardy from "Inception" to play a role in "The Dark Knight Rises" and there's rumors flying around that Nolan has been interviewing Hollywood's elite young actresses lately for the movie. Catwoman?
Also, Nolan talked about how important the Harvey Dent (Aaron Eckhart) character was in the last film, so maybe Two Face will return from the dead. We'll just have to wait until 2012 to find out.