The XenCenter released with XenServer 6.5 allows updates to be applied to all versions of XenServer (commercial and free)
With XenServer 6.5 patching and updating via the XenCenter management console (enabling automated GUI driven patch application and upgrades) is supported with the comercial and free XenServer versions.
XenServer 6 introduced the Rolling Pool Upgrade Wizard. The Wizard simplifies upgrades to XenServer 6.x by performing pre-checks with a step-by-step process that blocks unsupported upgrades. You can choose between automated or semi-automated, where automated can use a network based XenServer update repository (which you have to create) while semi-automated requires local install media. There are still manual steps required for both approaches and no scheduling functionality or online repository is integrated.
Citrix, XenServer/6.5, Commercial Edition
Hypervisor Upgrades, Updates and Backup, Management