If the current crop of rumors is right, then we can expect The Justice League to be much less gritty than what we’ve seen with movies like The Dark Knight Rises. According to Latino Review (who tend to be correct with these sorts of things), it’ll be based on Justice League of America issues #183-#185 which were written in the 80’s by Gerry Conway and illustrated by George Perez. Here’s a summary of those issues from the DC Wikia.
“On their way to their annual joint meeting, being held this year simultaneously on Earth-1 and Earth-2, several members of the Justice League and Justice Society are abducted via the Transmatter to New Genesis, home of the New Gods (as seen in New Gods, Forever People, and Mr. Miracle). The New Gods seek their aid after the [remaining] populace of New Genesis has been kidnapped and enslaved by the minions of Apokolips, the evil world that is New Genesis’s counterpart, and they reveal that Apokolips’s new allies are the members of the Earth-2 Injustice Society. The heroes split up into teams, composed of one JLA member, one JSA member, and one ‘New God’ each, and speed to various locales to undo the Apokolipsians’ evil, only to discover that their ultimate plan is the revival of their late leader, Darkseid.”
I’m sorry, what now? I had to read that twice to take it all in, but it’s the polar opposite of gritty reality even though there’s no telling which of those story elements might make it into the film and which are not even being considered. Still, even with the more fantastical elements toned down, this has the potential to be very different from the superhero movies of the last few years (if the information is correct that is).