Yeah, it's going nowhere if you had to ask me. We will get the same end game with Goblin, but the girlfriend will die this time. With any luck, Venom will get shoe-horned in part 3.
They should have taken a Harry Potter approach. Lock down young actors, like 18-19 year olds, for 5-6 movies. You don't go Twilight with every movie, and the franchise gradually maturates for audiences of all ages. Potter did this perfectly, not only maintaining but growing business without alienating the built in fan base at any point.
With that said, I don't think second tier villains like Electro and Mysterio do it for audiences either. You want to see the iconic villains, not an episode of the animated series. Voldermort was the villain people wanted to see. Not the bozos and side players. Now TDKR faces the same problem. Bane is solid, but not in the same class as the first three villains. At least Catwoman is in. Plus I don't believe Riddler or Penguin would have added anymore to the hype, which is still amazing. It's the Joker and then there is everybody else.
Spiderman has depth in the rogue gallery, but Goblin, Ock, and Venom blow the rest of the field out of the water. These are the villains people expect in a 200 million dollar film.