Idris Elba would be the perfect John Stewart, wow I can't believe I never saw that one before..
Also from what I have read on the interwebs, which never lie, is they plan to film the Man of Steel sequel and JL movie back to back. Releasing them a year apart, having the characters introduced in the sequel then a big cliff hanger that runs right into the JL movie.
I for one agree with this tactic.
Article discussing why this delay isn't a bad thing:
http://www.comicbookresources.com/?p...ticle&id=50455