Moviehole spoke to the Green Goblin himself about Spider-Man 3:
Speaking about repeating yourself, there are all sorts of rumours about Spider-Man 3 and Hobgoblin, and you had a cameo in the last one. Did Sam (Raimi) come to you about maybe doing your thing or are you going to try to stay out of this one?
Not yet. I like Sam a lot. I like Sam a lot. I’m not floating a balloon but I would guess that if he’d ask me to do something, I’d probably do something, but you know I feel patient. If there’s something for me to do, I’d probably be here but if not it just means it doesn’t make sense to be the goblin anymore.