A few weeks ago, the rumor mill went crazy when it was 'revealed' that Darkseid would be the villain in the upcoming Justice League film. This was never confirmed by the studio and has since stayed a questionable rumor. Today, the same source of the Darkseid rumor, Latino Review, alleges that the film's script by Will Beal will be specifically based on three issues of the Justice League of America comic.
Released in 1980, issues 183-185 were written by Gerry Conway and drawn by George Perez. In the comic, Darkseid is planning to destroy Earth and put his home planet of Apokolips in its place. The story not only contains the Justice League of America but also the Justice Society of America from Earth-2, as the two teams were planning to meet up when Darkseid initiated his plan.
Again, treat this strictly as a rumor for now because not much is currently known about the upcoming film. No director is attached to the project and it remains to be seen if 2011's Green Lantern or next year's Man of Steel will tie into the film, though Zack Snyder recently said that his take on the iconic character would "keep them on course" for a 2015 ensemble film.