According to The Hollywood Reporter, Nolan, who is on a much needed vacay, has yet to commit to the daunting task. In the article, THE DARK KNIGHT producer Charles Roven says:
There are a lot of us who emotionally would love to do it, but it's really Chris' call. Chris is the kind of filmmaker who just doesn't think about the next movie before he has completely finished the movie he is working on. When he comes back, we will see how he feels.
I must say I really hope he comes back and makes one more so it is like a trilogy.However with that being said If he does come back I can't see the next film topping the TDK.To me the TDK was probably the best superhero movie of all time.Everything about it was great,the story,characters,visuals,performances and so on.Even more so you cannot bring the joker back for the simple reason that no one could top Ledgers performance(i don't care who you are).And excuse me while I barf at the rumour of Angelina jolie playing catwomen or johnny depp as the riddler.Nolan would never cast either of those two and thats not a knock on Depp(who I think is brillant).They are names that would be bigger than the movie.So in closing I hope Nolan makes the third one but it very careful (not that I doubt Nolan)with it cause living up to the TDK is impossible.