The first DC animated film of 2014 has been officially announced as Justice League: War, which will adapt the Justice League: Origins story which kicked off DC's New 52 line in 2011. Fittingly, Flashpoint transitioned into the new 52 in the comics and it remains to be seen if we are now entering a rebooted film continuity. Worlds Finest has additional casting details.
My feelings are a bit mixed. I love me some Darkseid, but the comic arc was a bit superficial. On the other hand, it was basically written and drawn begging for an adaptation. Seeing as how we haven't really gotten a great JL origin since the Justice League animated series pilot, this could be a decent flick. Oh, and I love me some Darkseid... or did I say that already?