There's going to be six.
Tobin Bell has stated that he was signed on for a total of five sequels,[7] and producer Oren Koules confirmed on June 22, 2007 that both Saw V and VI were being written at the time. The authors of the scripts include Marcus Dunstan and Patrick Melton, as well as Thomas Fenton. The name Brennan Nold was mentioned by Lions Gate founder Jon Feltheimer in an interview, however he ended up having no involvement in the film.[8][9] Saw V started filming on March 17, 2008, while it started post-production on April 28, 2008..[2] Costas Mandylor has signed up for the next installment in the horror franchise along with main character, Jigsaw, portrayed by Tobin Bell.[10] Saw VI will be directed by Kevin Greutert, the editor on all the Saw films to date.[11]
Taken from wikipedia. Stupid forums won't let me post the link because of parenthesis
I can't wait until the Saw video game coming in 09.