Great news!!! Slackware 13.1 has been officially released. In the last few days, there has been no activity in -Current tree and they have prepared to put the ISO into replication phase which will be used for pre-orders in Slackware Store.
As usual, you will not find official ISOs in any mirrors now, but eventually there will be an ISO on the mirrors site within few days. For now, get the ISOs from torrents located in the main page of Slackware.
Read the ANNOUNCEMENT or the RELEASE NOTES and also CHANGES_AND_HINTS