MSP upgrades to VSM7 are supported, but you must engage Cisco as part of the upgrade/migration process. New appliances would be shipped with VSM7 already installed (at least this is my current understanding). If you want an official answer from Cisco, I'd recommend starting at the PDI helpdesk:
http://www.cisco.com/web/partners/tools/pdi.html
... and getting a conversation started with them.
Best of luck!
Scott Olsen
Solutions Specialist
Bulletproof Solutions Inc.
Web: www.bulletproofsi.com