Drew McWeeny at HitFix seems to think it's a possibility. According to him, JGL will definitely be making an appearance as the new Batman in JUSTICE LEAGUE, if his sources are to be believed. It makes sense. Christopher Nolan's Batman Trilogy has made insane amounts of money for Warner Brothers, and they aren't ready to leave that series quite yet. Drew states that it's a distinct possibility that at least one other character may be returning as well - Jim Gordon, perhaps? Drew speculates on a possible end credits scene in MAN OF STEEL that would bring the two sagas together. Go read it.
I'd have no problem if this were true. Obviously THE AVENGERS has changed the game in how these movies are made, and Warner Brothers would be wise to take a page or several out of Marvel's book. It's very interesting to me that if this is true, this would be a merging of these worlds - Zach Snyder's MAN OF STEEL and Nolan's Batman Trilogy, and that Gordon-Levitt wouldn't be playing Bruce Wayne at all. And yet... I'm also a little disappointed that there wouldn't be other versions of Batman out there. I'd love to see a different take on the character in a few years - something along the lines of the animated series, or just something different cinematically that we haven't seen before. JUSTICE LEAGUE would be different than what Christopher Nolan did, but it would also want to separate itself from something like THE AVENGERS.
This may be speculation or it may be accurate. I tend to trust Drew's sources on this matter - he's been right way more than he has been wrong - and so I'm sure this has some degree of possibility to it. What I'd be REALLY curious to know is if this sets up a live-action THE DARK KNIGHT RETURNS somewhere down the road, with an older Christian Bale returning to the cape. Dare to dream, huh?