http://www.slashfilm.com/article.php/20060824spiderman4-confirmed
QuoteMarvel Studios has confirmed that Spider-Man 3 won't be the last in the series.
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"There will be many more Spider-Man films to come," Marvel Studios' Producer Kevin Feige told MTV. "We already have stacks of ideas for the next one because of the wealth of stories in the comics. We could be making Spider-Man movies for the next 20 years, based on the 50 years of Spider-Man history we have."
Sounds like Saw. I read reports they had 7 scripts for the Saw franchise ready to go.