Maybe they're rally interested in doing a JLA movie, they could spin off whomever play Batman in that movie into a new series of Batman movies. That'd be something of the reverse of how Marvel Studios built up to the Avengers movie.
And that's I think what they're likely to do. But I'm just not sure if that's the best way to go. I personally felt that The Avengers would've fallen completely apart if it hadn't been for most of these characters' introductions in their own films. With some of the JLA characters being much more unknown to a general audience (any myself, frankly), how can you do them justice AND Batman AND Superman?
Besides, how much Batman could there even be in such an ensemble piece?
But the studio seems hellbent on replicating the Avengers success with their own brand, so this is what we'll get. I myself would like to see another fanciful Batman - not a campy one, mind you, but one that is both dark and comic-book big, allowing also for the somewhat supernatural elements. Sorta like Tim Burton's approach, but without the Burton craziness shtick. A gothic Gotham (gargoyles, I need gargoyles!), a noir-ish quality, Batman as detective, mystery and a great villain, etc. So many of the comic books have done that so perfectly: The Long Halloween and Dark Victory, for example. There's gotta be a way to do that today, even now that the "near-real world Batman" by Nolan is all the rage.