From Scifiwire:

Batman Begins producer Charles Roven told SCI FI Wire that the cast is signed on for a sequel, the script is in the works, new cast members are being discussed and the only delay is an OK by director Christopher Nolan. "We all hope there is going to be another one," Roven said in an interview for the upcoming Terry Gilliam film The Brothers Grimm, which he also produced. "We're waiting for Chris Nolan to declare himself. We will do it after he does that."

Batman Begins star Christian Bale has signed on to reprise the role of the seething and dark Bruce Wayne/Batman, as have Michael Caine as the butler Alfred, Katie Holmes as the love interest Rachel Dawes and Gary Oldman as police detective Jim Gordon, Roven confirmed.

But Roven added that it's too early to talk about new cast members. He discounted rumors that The Daily Show's Steve Carrell is up for the role of the Joker. Roven is working with Carrell on the big-screen version of the TV spy comedy series Get Smart and said it's way too early to talk about new cast members for the as-yet-untitled next Batman film.

Roven said that it would be possible to proceed with another Batman movie without Nolan, but added that he would prefer Nolan to do another one.

"The point is that the studio owns the franchise, and they can do without any of us," Roven said. "But it was a spectacular experience with Chris [Nolan], and he kept everyone involved and was very collaborative. So we hope it will happen again with him."