The FAQ only mentions 2 players.
A few random thoughts: Animations look a bit janky. Going to be interest to see how they make the 3 melee characters feel different from each other. I assume it's in the comics but the soul jumping thing just looks ridiculous.
I saw something on Twitter that the PS store had it listed as 1-4 player coop. Someone in the comments varified that it was indeed there. Speculation was that was just a * up though.
I agree the soul jumping looked ridiculous, I'm not familiar with the back stories or comics though.