shouldn't it be fine if the destination host has enough licenses to apply to the vMotion'd VM?
"For Windows Server software, except in a few cases (see “Assignment of Licenses” above), licenses may only be reassigned to new hardware after 90 days. This, however, does not restrict the dynamic movement of virtual OSEs between licensed servers. As long as the servers are licensed and each server individually does not run more instances than the number for which it is licensed, you are free to use VMware vMotion and System Center Virtual Machine Manager to move virtualized instances between licensed servers at will."