Updates to Raspbian packages can be installed via apt-get as usual. The same goes for packages specific to the Revolution Pi, those are made available through a separate apt repo: https://packages.revolutionpi.de/dists/

Upgrades to new releases can be performed either with an in-place "apt-get dist-upgrade" as is customary on Debian-derived distributions, or by creating a backup image of the eMMC, flashing the new image, then copying over any customized config files from the backup.