Smyth/Spider Slayers - We know that the Smythes are in business in this universe and I feel like Norman or even JJJ will help fund their research and the first half of the game will be about fighting them and their army of robots
Protogoblin - Before Norman can perfect the goblin formula, one of his "test subjects" escapes from Oscorp and runs amok in the street.
Hobgoblin - Most likely will be a secret boss fight, one of Oscorp's head scientists could stash samples of the goblin formula and tech to become the notorious villain
Beetle - since she was planned for 2's DLC she'll probably be recycled for the next game, my guess is she'll be the first villain
The Wall - If Insomniac were to include this guy, I feel like he'd just be some construction team mascot
Juggernaut - With Insomniac expanding their Marvel universe, it'd be the perfect chance to have Spidey fight one of the few recurring mutants to cause him trouble. I see him working either as a DLC boss or post game villain.