The Avengers have finally been brought to life and it's made all the money everyone expected and then some. It would be foolish of us to think that WB isn't planning to follow in the same footsteps as Marvel/Disney and release a series of films for their heroes leading into a Justice League film. There's no official word that this is happening, but if you don't think they're seriously considering it that would be a mistake. Who knows, maybe next year's Man of Steel is going to lead into the Justice League movie. If it doesn't, WB is shooting themselves in the foot.
I wanted to do a piece that was a 'map' of sorts on how WB could mirror Marvel's success at the movies and which characters they could do it with, but decided in lieu of that we'd just decide which characters need to be in the Justice League film and who should play them.