noone knows for sure who will be in spiderman 3, all i can think of, spiderman 2 ending with harry finding his dads secret stash of the green goblin accessories, therefore i can only imagin that harry will be as teh green goblin II in spiderman 3 because there not exactly going to leave harry on a cliff hanger and forget about him during 3 hours of spiderman 3 are they?
unless they decide to put green goblin and Venom in spiderman 3 making it a triple fight like venom and greengoblin II team up and make a deal with each other etc,,, that would be pretty cool but i guess we will have to wait until 2007 :|