Call of Duty: Modern Warfare 3 Elite memberships until March 1, 2013.
The same services (which include things like clan support, Elite TV, and a few other options) are going to be free for everyone in Call of Duty: Black Ops 2. Given the issues Elite had at launch, it seems sensible to let premium subscribers keep playing without paying any more.
This leaves one question, however: What will happen to MW3 Elite Premium subscribers when subscriptions do end on March 1, 2013? A FAQ on the official website says Activision isn't taking any new subscribers at all, since new DLC is no longer being offered. We've contacted Activision for comment and will update if we hear back.
Update: Activision says that "when your Call of Duty Elite Premium membership subscription term for Call of Duty: Modern Warfare 3 ends – whether on March 1, 2013 or after, your formerly "Premium" Elite membership for Call of Duty: Modern Warfare 3 turns into a "Free" Elite membership for Call of Duty: Modern Warfare 3." So users will still have access to all of the features of MW3 Premium, but they won't have to pay. Feel free to keep shooting!