Spoilers for the uninformed,
During Batman's nightmare, he dreams of a possible apocalyptic future (or alternative universe) where Lois Lane is believed to be killed, and Superman becomes a violent and tyrannical ruler and creates a stormtrooper army to enforce order and weed out dissent. Batman, in his desert garb, meets with his fellow soldiers to retrieve more kryptonite to kill Superman. However, he is deceived and the Supermen army along with Parademons (minions of supervillain Darkseid) take Batman and his fellow soldiers as prisoners of war. He is later chained up when Superman arrives and his stormtroopers bow to him. Superman uses his laser beams to kill the other two soldiers and pulls off Batman's mask. He says that "she" was his world before violently punching Batman through the chest, and he wakes up.
I don't know about you, but that's almost the entire premise of the 2013 fighting video game Injustice: Gods Among Us. In the game, the Joker tricks Superman into killing Lois Lane and his unborn son, and then detonates a nuclear bomb in the heart of Metropolis. With the Joker in prison thanks to Batman, Superman arrives and punches the Joker through the chest, killing him, thus creating an alternate universe where Superman becomes a violent and tyrannical ruler. He vows to permanently end all conflict by creating a totalitarian world, enforced by his stormtrooper army and the help of Wonder Woman, Black Adam, Yellow Lantern (Hal Jordon with a yellow power ring), and Cyborg among others, who end up on his "good" side. To help him overthrow this corrupted Superman, Batman opens a dimensional portal and pulls in the Justice League from the normal universe, including another Batman, Green Arrow, Green Lantern, Aquaman, and the normal Superman among others.
I really, really hope that this isn't the angle that their going with for the Justice League movies, and that it's really an alternate universe that the Flash emerged from in the scene right after. If so, then it might make things interesting if Darkseid manages to manipulate dimensional travel so that the Justice League (Superman, Batman, Wonder Woman, Aquaman, Cyborg, and Flash) would have to fight Darkseid and their evil counterparts.
What are your thoughts? Would this make for a good premise for a Justice League movie or is it franchisicide for a prospective DCEU?