Let me explain.
The Original Justice League members are Superman, Batman, Wonder Woman, The Flash, Green Lantern, Aquaman and Martian Manhunter.
We already have Superman (Henry Cavill), Batman (Ben Affleck) and Wonder Woman (Gal Gadot) locked in. Insiders say Flash is a lock, too. Rumours abound about Denzel Washington as Green Lantern and Jason Mamoa as Martian Manhunter as well. That just leaves Aquaman. It should be noted that a recent mailbag from Batman on Film states that neither Martian Manhunter or Aquaman are in the movie. Furthermore, it also states that from what they have heard, this is still a Superman movie. Take that for what you will.
This looks to be Warner Brothers and DC Comics play in the comic book movie market to take back some of the immense share that Marvel has carved out over the last few years and it would be a bold play.
Where Marvel did individual hero movies first and then brought them together into The Avengers movie, it looks as though DC is doing the opposite — starting with a Justice League movie and then, most likely spinning off individual movies for those characters that do well in the movie.
WB has also not announced an official title for this movie, which starts filming in February. They refer to it as Batman Vs Superman, even going so far as to register several website names with variations on the main two characters names. It seems unlikely that any of these will actually be the titles, at least not in my humble opinion. Wouldn't it be an earth shattering announcement to release the name of the movie... and have it be "The Justice League"?
Our hope is that Henry Cavill does not get shortchanged for screen time. Superman is after all, the leader of the Justice League. And, if MOS2 turns out to actually be JLA, then we hope Henry gets his due in a real sequel to Man of Steel.