Mark Millar is probably laughing his ass off at this rumor. Warner Bros. hired Will Beall (Gangster Squad) to hammer out a Justice League script a year ago, and so far details on it have remained almost completely under wraps. Makes sense, especially with the studio searching for a director and trying to figure out exactly what the approach is going to be, or if it will happen at all. But now a story has emerged which indicates there may be some trouble behind the scenes, at least on Beall's end.
Bad Ass Digest says they've heard from multiple sources that Beall's script has been thrown out, and the search for a new writer has begun. If you'll recall a few weeks ago we heard a rumor that David Goyer (The Dark Knight Trilogy) had taken over rewriting duties, but this makes it sound like a totally new draft is in the works. The reason for the change? The general consensus is that the script was "terrible", and suffered from studio meddling which involved heroes beyond the core five(Superman, Wonder Woman, Green Lantern, Batman, The Flash) being dropped and added at will. Last we'd heard, Beall's script involved the team gathering to battle the threat of Darkseid, so it remains to be seen if that aspect stays in play.
All of this rumor for now, but supposing it's true, this would go a long way in explaining why they're waiting until after Man of Steel hits before making a final decision on Justice League. It's also probably a reason why they've been unable to secure a director. Right now it's looking like that 2015 release date is nothing but a pipe dream.