Or, are you saying that I need to purchase new 11d remote agents whether it's an upgrade or a new install?
Correct. No matter how your media server gets to v11d, ALL agents it talks to must be v11d agents to meet the Symantec Licensing Policy. Older agents will physically work, so you don't have to boot 25 servers at one time, but you will need to upgrade all agents, sooner or later, to stay legal