There's a rumour going about that the director for Saw IV is close to being signed.

The production designer on Saw II, III (Filmstalker review) and Skinwalkers, who also served as second unit director on Saw III, David Hackl, is set to direct.

The rumour comes from Bloody Disgusting through AICN, and according to BD they...

...checked in with Bousman who had this to say, "I fully support the idea of David Hackl directing the next 'Saw' film..."

Yes, and let's just be firm, they asked Bousman what the thought if Hackl directed, at the moment he is in talks and hasn't signed, so who knows. As I said before I think they can pull this off, but they really have to concentrate on the cleverness of the traps, and not just throw traps at the audience.