Goyer talked to Premiere magazine and provided this info:
As read in the latest Premiere magazine featuring Batman Begins, Goyer states the next film will involve the Joker … “The next one would have Batman enlisting the aid of Gordon and Dent in bringing down the Joker- …. but not killing him, which is a mistake they made in the first one”. The article then says that “In the third, the Joker would go on trial, scarring Dent in the process.”
Sounds like a trilogy to me. Click here to read the source article from Ain’t It Cool News.