We all know Harry is going to be the Goblin in the second Spider-Man film. I think there is overwhelming evidence here:
And here:
Many people believed coupled with many different hints at Gwen's death in this film such as:
Gwen Wearing the Same Outfit from the Night Gwen Stacy Died
Spider-Man's catch in the same way he caught Gwen there
and Spider-Man fighting the Green Goblin in the same location:
However, I think there is something we're missing here. First of all, doesn't this seem like an odd thing to almost give away in the first trailer of the film. Unless...this whole thing is designed to fake us out and make it seem like Gwen is dying in this scene thanks to the Green Goblin, but, really, that comes later in the film, after lulling us into a false sense of security.
Let me elaborate. There is a scene in the trailer where Peter tells Gwen that this is his "path":
I feel like this is going to be a beautiful pay off to the promise he made Gwen's dad. Before, he had thought that he could keep her safe but when Goblin kidnapped her and nearly killed her, Peter realized that it would be selfish and irresponsible to stay with her. He tells her that he can't give up being Spider-Man, so he has to give up being with Gwen. Much like Spider-Man 2...without the happy ending.
Peter leaves Gwen at the bridge and then leaves again to go clear his mind where Gwen stays at the bridge, contemplating the situation:
However, Peter had managed to defeat Norman's son, getting rid of Norman's last chance for a cure. Norman is desperate and decides to use the unfinished Goblin serum on himself to give himself the strength to at least exact revenge. However, Norman's disease mutates the Goblin formula, giving life to this:
Spider-Man catches wind of this and heads to the George Washington Bridge and finds Gwen, unconscious, on top of the bridge, with Goblin holding her. Peter pleads with "Harry", thinking the mutation must've only progressed further. Green Goblin only cackles and tosses Gwen off the bridge. Spider-Man leaps over to catch her but he only snaps her neck by catching her by the foot.
Peter threatens Harry and promises to kill him. After bringing Gwen down to the first responders, Peter goes to Ravencroft to figure out how Harry escaped but finds Harry in his new cell, only mutated to his skinny, green form. Peter beats Harry and asks how he managed to break out of his cell.
However, Harry is able to convince Peter that he never broke out and that he was in the cell from the moment Peter put him in there. Peter breaks down and asks himself who the new Goblin is.
An after-credits scene shows Goblin lurking in the alleys now, as Norman Osborn, not Harry Osborn.