On the topic of Doomsday and Lex Luthor, which will be the main villain? I doubt that they are trying to repeat Spider-Man 3 (I'll looking at you Amazing Spider-Man 2), so you would think there would be a MAIN villain. Maybe Lex creates Doomsday, maybe Lex is just a bystander, maybe they will cut out one of them, but I doubt they will BOTH be major villains.
As for the heroes, if this does turn out to be the Justice League movie, it looks like it will be using the league from the animated series with Superman, Batman, Green Lantern, Wonder Woman, the Flash, Martian Manhunter, and Hawkgirl, as opposed to the New 52 league which replaces Martian Manhunter and Hawkgirl with Cyborg and Aquaman. It may also be a mixture of the two. Or it could be Batman and Superman fighting, which, when you think about it, would be boring since there would be no villain.