Sounds like Blizzard are gonna start picking people for the Cataclysm beta soon:
To ensure you’re opted-in and eligible as a potential candidate, you’ll need a World of Warcraft license attached to your Battle.net account, have your current system specifications uploaded to the Battle.net Beta Profile Settings page, and have expressed interest through the franchise-specific check boxes.
To see the whole blue post, which isn't much more than what I quoted, you can go here
. To make sure you're opted in for the beta, go into the beta profile settings in your battlenet account, and make sure "Warcraft universe" is ticked (and that you've uploaded your system specs and jumped through all the other hoops they want you to). promoted forum item