I may not be on the Erron Black boat, but seeing a screenshot, leaked or not, that has him blasting his guns in his opponent's face pretty much says "I'm in the game." We haven't seen Liu Kang at all yet but he's already been confirmed a hell of a long time ago. I don't think Netherrealm Studios needs to officially confirm every single character before revealing them in the stream just to make the fans go, "Okay, they're in" after having a screenshot get leaked of them.
They're either going to touch a character that hasn't been seen yet, or they'll touch Goro finally. I'm leaning more on the side that they might finally do something with Goro, but I've seen it get said by others plenty of time and have yet to see anything get done with him.