We are planning for CUCM upgrade from 9.1.2 to 11.5. But I have some doubt regarding the licensing part. In the current version we have ELM for license management, which indeed is going to change to PLM in 11.5. Will there be any impact on the current license after upgrade. Please provide your views on this.
If you want to play super safe you could install a standalone 11.5 PLM, and get your licences migrated prior to the upgrade. Then when you upgrade just point your publishers to the new PLM instead of the old.