Steve G. wrote in comments that "Emma Stone is so perfect for the part that I doubt it'll happen." Apparently, we get to be proved wrong, because it's so on. The question now becomes who plays Gwen Stacy, and what the hell do they do with her. The misuse of Bryce Dallas Howard in a throwaway version of that role in Spider-Man 3 was a perfect example of the problems with that movie: it was overstuffed and inattentive. I still think it would have been a better movie if it just focused on the Sandman, coming full cycle with Spider-Man's creation myth, notions of justice and understanding of history, and then made a truly terrifying Venom movie. (Topher Grace is congenitally unterrifying. As is Philip Seymour Hoffman.)
One of the best parts of the panel on superheroes and New York I went to last spring was the discussion of Gwen Stacy's death. I tend to think a Spider-Man reboot should contain some real loss that isn't just part of the origin story. Uncle Ben has to die for Spider-Man to live, so it's not particularly shocking. When Harry bit it in Spider-Man 3, it was kind of a relief: he'd become less a character than a collection of personality traits and an obstacle to the inevitable Peter-MJ marriage. So maybe what a new trilogy should build up to is Gwen Stacy's death. And it should count, this time.