I doubt Spiderman 3 will be the last in the series, unless the entire cast refuses to return to make another movie. I read an interview with someone involved in the series months ago, and they said that the idea is to create six Spiderman films. It seems like a bit of a stretch, but as long as the movies continue to be well made and popular, I doubt any of the stars would leave the project. Raimi might, though. Having Venom as a villian will be amazing. As soon as they make a movie with Carnage, my fanboy dreams will have come true.