All UCMs, Slaves, and new keypad models KT03 and KP06 are already at version 6 or 7.
Those with firmware 5 can be upgraded to version 6 or 7 by using the UCM firmware programming cable
Version 6 or 7 modules can be upgraded without needing the firmware programming cable as shown in http://www.comfortforums.com/forum92/3400.html
as mentioned in that post you upgrade to the latest firmware by right clicking on the selected module and selecting "check for updates" so it is very simple.
Comfort and UCM firmware should be version 7 in order to upgrade other modules firmware by Comfigurator. The other UCMs, KP06, KT03 etc can be version 6
Eventually all modules will be version 7 but except for Comfort and the programming UCM, the difference between v6 and 7 is not so significant except for new features
It is recommended that firmware be upgraded so that future upgrades are much simpler