There are not going to be further releases of 6.0.x. If you need a supported 6.x-based release, you can purchase a JBoss Data Grid subscription at http://www.redhat.com/en/technologies/jboss-middleware/data-grid
The supported community releases are 7.0.x and 7.1.x (and soon 7.2.x).
Tristan, thanks for being active and responding to people's questions on this forum, it is a big help. Since upgrade to 7.x seems like the right thing to do, would someone on the team be able to add some instructions for migrating the old configuration files to the new format? A tool would be nice or at least an update to the 7.1.x upgrade chapter: