Spidey 4 in under discussion.
S3 was far too crammed, with too much going on. There was the Harry Osborn Goblin Junior story, Venom and Eddie Brock, The Sandman, and even Gwen Stacey, all stuffed into one film. There was at least one more or maybe two more they could have gotten out of this material.
Now we're left with the leftovers. Kraven The Hunter and one of the Vulture's incarnations are possible. They did a team up story, so that's one area to explore.
Then there's Electro. Or even The Scorpion, which gets more mileage out of Jameson.