Spiral: From the Book of Saw is reportedly the official title of Saw Reboot.
Spiral: From the Book of Saw sort of fits into the Saw 9 mythos, since it seems mysterious and a bit ambiguous, while still tied to the franchise as a whole.
The working title for the horror movie was Organ Donor and is still what is listed on the Wikipedia page for the reboot.
The reboot hits theaters later this year and there has been a ton of speculation as to what the official title was going to be.