According to reports at IESB.net, Christian Bale is not too keen on the idea of Batman being recast in the proposed JLA movie at Warners. Bale indicates that he was never approached and that he wouldn’t welcome someone else wearing the cowl. In the interview over at IESB, Bale's comments seem to indicate this.
Q: Are you doing Justice League after TDK?
IESB: Have you been approached for Justice League?
IESB: How would you feel about the studio recasting Batman for Justice League?
Bale: It’d be better if it doesn’t tread on the toes of what we’re doing, though I feel that it would be better if it comes out after Batman 3.
I like the idea of a Justice League movie. I also like the idea of throwing as much money as possible at Bale to get him to appear as Batman in the film. Bale has made the character his own and I'm not sure anyone else could do it justice (sorry about the pun). A JLA movie is almost guaranteed bank for WB, so they need to pony up the cash to both Bale and Brandon Routh and make the movie an event. It is also being reported that Ryan Reynolds wants to put on the red tights and play Flash... the potential cast for this movie gives it the possibility of being awesome.
Regardless of what happens with the JLA movie, Warner Bros. would be absolutely insane to upset the people who are currently in charge of the Batman franchise. Christopher Nolan and crew knocked it out of the park with the original and appear to be making all the right decisions on the sequel.