I'm not sure how they can really fit Gwen Stacy in -- is there a point in having a romantic rival when Spider-Man is never ever going to leave Mary Jane onscreen? I remember when we all thought (or maybe it was just my corner of the Internet) that they would reverse comic book history, and kill off Mary Jane and hook Mr. Parker up with Gwen. (If House of M is to be believed, and it probably isn't, that's who he really wanted anyway.) Is there even any emotional impact if they kill off Captain George Stacy in a fourth film, as James Cromwell once said they planned on doing? Is the subplot of "I'm really sorry your dad died, my one-time love interest" really worth exploring? I could probably think more clearly if I could get the breakdancing scene out of my head.
Of course, this is all idle speculation when no official announcements have been made. And as for Sam Raimi he's now playing coy with MTV about returning to the director's chair, and says he wants to wear the Spidey suit instead. That's one way to cut the budget.