It appears the XenServer 6.5 has been released and it's quite a bit faster than 6.2 in many ways.
When I installed 6.2 I accepted the various defaults and end up with a system that is awkwardly partitioned. Root is rather small (and perpetually running out of space) while a 250Gb partition sits empty. To this end I'm thinking about doing a rebuild with v6.5.
I've been reading about the process and apparently you can't mix 6.2 and 6.5 in the same pool. If I take the pool members (3) out one at a time, rebuild them and put them in a new pool can I move the various VMs over?
EDIT:
To upgrade XenServer from 6.2 to 6.5 - start with the pool master and work your way through each server. If you've done a repartition you don't have to do the editing steps again - as long as you select 'upgrade' during the 6.5 install it won't repartition the disks.
The pool master and servers in the pool need to be the same XenServer version. To answer your question, yes you can remove one server at a time, upgrade, join the pool, then migrate the VM's. As always, make sure you make a backup first (export snapshots) before performing the upgrade.