I'm not sure how this works officially, but it looks to me like Slackware 13.1 has been released. The new slackpkg mirrors point to slackware-13.1, /etc/slackware-version shows 3.1, and there is a new root message after the last upgrade that says "Welcome to Slackware 13.1".
I think it's here. But as I have been keeping my systems up with current, through slackpkg, I don't think I have to do anything extra. This is nice. I like not having to do a big install, and still be up with all advances.
Only thing I am waiting for now is for a lot of other developers to adjust their code to the latest version of gcc. And I'm looking at the video libraries to make dvdrip work, and Digikam.