I'm pretty sure many of you will want to know if there's going to be an "Injustice 3". Well, I can't say for sure, but I'm pretty convinced it will. Question is, which ending of Injustice 2 will be canon then? Why the most optimistic people wish for Batman's ending to be canon, I'm more realistic; so I say the ending canon will be the one of Superman. Why?, easy, because this is the ending that promise the endless conflict of this reality will continue. Injustice is everything about continuous fights and deaths, which leads to a broken world and a hopeless future.
In the new comic crossover "Injustice vs Masters of the Universe", we saw the world of Superman's ending. People say He-Man will defeat Superman and free the world, but Injustice has proven never to be that easy. It follows the same structure that Injustice's comics (Years 1 to 5). Basically, the Insurgency tries to defeat the Regimen, but a secondary problem suddenly happens (in this case, Darkseid's attack on Greyskull) and both sides are forced to collaborate. But as soon as it's over, things end in a way that none of the sides end-up winning anything; and the weakest side (the Insurgency) ends up in the worst condition, only making the Regime stronger.
So, as far as I see, Darkseid will be defeated, but Superman will take advantage and the Insurgency will end up worse than at the beginning. In fact, something tells me Superman could even get his hands on the Anti-Life Equation; which is really bad. Seeing how people turned against He-Man at the beginning of the first issue for defeating a dictator could be a premonition of nothing good. Besides, there's an aspect of this ending that the comic seems to have forgotten: Superman's Legion of Super-Heroes. There's no sign of Superman creating this army in the comic, so the story could end up with the first clues of it.
With this, "Injustice 3" could be a war against Superman's army, who after conquering his universe, he puts his eyes in other universes; starting with the one of the heroes who defeated him in the first game.