This report from Aintitcoolnews.com:

"The next one will be it. I'm only contracted to 3 and don't see myself signing for a 4th or a 5th," says Dunst, emphatically. Asked if she would love to see her Mary Jane character killed off in Spider-Man 3, Dunst laughs. "It would actually be really interesting if SPIDER-MAN died. Why doesn't the superhero ever die? I think if Mary Jane was alone, pregnant and he died, she could give birth to a spider baby and carry on the series with another young boy or something like that. I doubt Tobey Maguire would come back for a 4th or a 5th either."

Just one more Spider-man?!

And look at her...  she's laughing at our pain!!!

-Bubs