Some potential bad news here, folks. As we have come to learn, WB have been waiting to see how Man of Steel performs box office/reception wise before they make any advancements on their Justice League project. The previously scheduled 2015 release is however in a bit of trouble according to Bad Ass Digest and their sources.
The script (from Gangster Squad's Will Beal) is apparently just "flat out terrible". So bad in fact, that sources are telling BA Digest that WB is losing faith in the project and may scrap it altogether. Other sources however, claim that they are not quite ready to throw in the towel and let Marvel win just yet.
The script is said to deal with Darkseid and the five core members that were recently confirmed by Latino Review (Supes, Batman, WW, GL & Flash). The sources are calling the script "half-baked from the beginning", and heroes outside the main five have been added and subtracted throughout development. It is due to this terrible script that WB have been hard pressed to find a director willing to commit to the film.
As is usual with these sort of things, its best to take it with a pinch of salt. One thing is for certain though, I wouldn't expect to see a Justice League movie to arrive in the summer of 2015 by any stretch.