On the day of writing, the newest version of Solaris 10 is u11 (1/13) and Cluster (for Solaris 10) is 3.3u2.
Cluster 3.2 is still supported by Oracle, but patches are no longer released. Update 11 for Solaris 10 is probably last Release of Solaris 10 and has some new features, which are not available if you only patching a system with Recommended Patches.
Before starting with upgrade it is good to check and fix any issues with current system and environment.
Please check a Cluster status, Quorum device status, running services, zpools, metadevices, metasets, hardware components etc.
If you have any issues, fix them before you start. Plan your Maintenance Window, make backup of your files and configuration.
Solaris 10 Release and Solaris Cluster 3.x upgrade + patching
