According to Bloody-Disgusting, Lionsgate may have found their director to help Saw IV. Here is condensation of what B-D has to say on the matter:
Both films were/will be Directed by both David Moreau and Xavier Palud -- two names you might never forget by the end of 2007.
What we've been told by numerous sources (that have all checked out) is that David Moreau has been at Lionsgate multiple times for meetings on the possibility that he MIGHT helm Jigsaw's next adventure (if he even returns). He is all but confirmed, but in heavy talks. No word on his directing partner Xavier Palud, who we would assume would join him at the directing post.
Lionsgate will release Saw IV on October 26, 2007.