According to NeoGaf user Backflip:
According to one of our sources, Injustice 2 is in development on PS4, Xbox One, and PC and should come in May 2017. The game should be announced between now and the end of E3: http://www.gameblog.fr/news/59264-injustice-2-bientot-devoile-d-apres-nos-sources
I'd create a new thread about it but I can't.