They are doing the Green Goblin again? 
yep, but I still hope they make room for other villains, if not in the 2nd one then the 3rd one. Electro and Kraven were always my favorites when I was a kid and like Robo said, doing Kraven would help make this trilogy more unique.
If they choose to borrow anything from the Ultimate universe, they should do Carnage since the Ultimate version didn't require much from the Symbiote Spidey/ Venom storyline. We don't need to see that again. Plus, Carnage's insanity also works for this "dark" thing.
If the sequel depicts Green Goblin basically ripping off the Joker, like Robo said, I will officially label this whole franchise a Dark Knight trilogy rip-off.