If we won't be seeing any Goblins, or at least any green ones, it's kind of pointless to have this thread.
There is no reason to kill Gwen if not to have the Green Goblin do it. If we gave that honor to another villain, it wouldn't be right.
The new series is going to built, I think, as more than just one trilogy. I'm thinking three films in high school and three in college.
If we are going to get Gwen as a supporting character in a large capacity, the only way to move from her as the only love interest to Mary Jane as the only love interest is to kill Gwen.
Also, if we are going to have Harry Osborn in the series....which is a must because he is Peter's best friend, there has to be Norman and there has to be at least ONE Goblin with hints at the Goblin legacy. This was messed up in Spider-man 3, they REALLY dropped the ball on a great set up of this legacy, no reason why this new series cannot rectify this.
We will probably get new villains. Lizard, Electro, and Vulture come to mind as sure fire possibilities. But- just like you cannot retell the Batman story without reusing villains like Joker and Two-face you cannot retell Spider-man's story without using Ock or the Green Goblin.
I sincerely hope that they do not let the previous franchise or the time that has elapsed between franchises hinder them creatively. They are using this reboot as a way to get themselves out of writing themselves into several corners in the previous franchise (introducing Gwen too late, killing Eddie Brock too early, and several others) it would be dumb to let the reboot itself be a corner to have to get out of.
They should have free reign on the story and characters and just make the best films possible. If they do that, it doesn't matter if these are villains we've seen before. If they are presented in a new way, with different dramatic weight behind them--it will work.
-R