We want to confirm that, at this time, all World of Warcraft Annual Pass
subscribers have been invited to the Mists of Pandaria beta test, with two groups of exceptions. One exception group are those who purchased an Annual Pass on or after April 18, and will receive their invite in a future wave. The second exception is a small list of remaining accounts from previous waves that encountered an error, and will be properly flagged for beta access as soon as we can resolve the issue.
If you haven't yet purchased an Annual Pass, you still have time to guarantee your spot in the beta by signing up for a year agreement
(link) before the offer expires on April 30. Those taking advantage of the Annual Pass receive Diablo III for free, access to the Mists of Pandaria beta, and the exclusive Tyrael's Charger
flying mount for your World of Warcraft characters.