Or, if this film is a continuation of the original seven film run, then there’s a chance that the ending of Saw III could be retconned, showing that his surgery was nothing more than a sham to take out Jeff and Amanda, the maze rats du jour of that particular entry.
Again, there’s a lot of room to think with the potentials for Saw: Legacy, at least until an official press release is dropped dispelling any of our notions.
With no other original cast members returning from any of the Saw movies, there’s always the possibility that this film is a reboot and John Kramer/Jigsaw will be restored to square one, free to commit all of the morality induced entrapment he wants.