Injustice 2 has been confirmed for mobile devices. NetherRealm studios Ed Boon took to Twitter to deliver the news: 

While we wait on "more info" let's take a look at what the pictures tell us. First, the most obvious thing, it looks like you will have three heroes at your disposal during matches. That feature differs from the console version which is the traditional 1v1. Second, WHO TF IS PREDATOR BATMAN?!

Check the second picture in the top left corner. I did some digging and nothing came up but the Batman vs. Predator comic book series. It could just be Batman in an alternate outfit, but if it's Batman with Predator-like tools, I'm so down. I feel like I'm setting myself up for a big let down here. 

In either case, no real details to go off of other than those screenshots, but we'll let you know when there's more to know.