Spiderman 4 ?

Although Tobey McGuire did say that Spiderman 3 is the last Spiderman movie he'll make, in an interview with SCI-FI Wire:

"It all depends on if there's a story worth telling. I feel very proud of the three movies that we've made. I feel like the stories all deserve to be told, and, you know, if they come up with a good movie, and the whole team wants to get back together, and we feel like we can make a good movie that's worth making, then I'm up for it."