Well, it has been
released as Slackware
13.37. The "37" comes from the kernel version being used. I would have gone to version 14 for such a change, as the concept doesn't really fit with 13.0 and 13.1 ... not to mention that 13 is an unlucky number
(or, perhaps, gone backwards and started filling in at major version 5 that was
skipped).
I use and like Slackware, but see no need to upgrade my systems now.