What do we know about the Justice League movie coming out in 2015? Well, we know the premise: Batman, Superman, Green Lantern, Wonder Woman, Aqua Man, and the Flash join forces to fight evil. Excellent. As for all other details, they seem to still be in flux.
The omnipresent rumor mill of the interwebs has been trying to tie the Dark Knight Rises to Justice League but that link seems tenuous at best. The virtual murmur was that Joseph Gordon-Levitt would play Batman, but it seems that rumor has been put to rest. Gordon-Levitt's representatives "refuted the rumor entirely," which of course made some even more sure of its validity.
At the end of The Dark Knight Rises Gordon-Levitt was looking like he'd become Robin, so suddenly throwing him into the role of Batman honestly didn't make that much sense, cross-movie speaking. As Warner Brothers is the driving force behind both movies they could, in theory, tie the two pictures together; but if Christopher Nolan has anything to say about it they won't be doing that.
The other film franchise that is being potentially linked to the Justice League is Man of Steel. The Superman film stars Henry Cavill in the title role, and there are talks that this could be fodder for a Justice League tie in.
For now, the speculation will have to continue. It seems unlikely that we will see Gordon-Levitt in a Justice League role, but Henry Cavill is another story.
Warner Brothers plans to shoot Justice League in 2013, with a release date planned for summer 2015.