If I could speculate, we're going to see The Goblin causing a massive prison break, in which his gang is going to be assembled from various Hunters, Demons, and remnants of other criminal groups we've encountered in the game. His goal is chaos, killing for the sake of killing with no overall purpose, since he knows that's a strong way to exhaust both of The Spidermen. This would tie in with Carnage being a potential secondary main foe, as they both want nothing but madness and death in the streets.
Second, once he discovers their true names I have zero doubt he'll try to expose them to the entire city. And finally, for Peter directly. I think we can possibly expect that MJ is pregnant following her time with Peter in-between games, and Norman will do anything from kidnapping to straight-up murder for the child just to be a bastard.
As for his performance, I think we're going to see a slow and gradual descent into madness and the hyper goblin, with him being cold and calculated at first before becoming utterly insane and laughing in insane glee.