9 Justice League
Creating a Justice League film is very simple: just replicate in live action the cartoon, specifically the Justice League Unlimited version that featured dozens of superheroes.
I suspect that this film coming to fruition will depend on the performance of The Avengers next year. If it blows up big then DC may be extra inclined to try and emulate Marvel’s success with a team-based superhero picture.
With Justice League the potential for celebrity cameos as some of the more obscure DC Comics heroes could make for an especially fun Summer picture.