These forums are open to the general WoW population, and are NOT the alpha / beta forums. The alpha has NOT begun yet. But things are at least moving in the direction of more Cataclysm presence in WoW's official community.
With Cataclysm expected to be released in 2010 (remember, according to Mike Morhaime, not us), we should start seeing greater details about what was announced at BlizzCon in the next couple months. Lots of good stuff to know, and hopefully this forum will be a conduit for Blizzard's old top hats like Ghostcrawler to begin some more detailed information dissemination.
World of Warcraft: Cataclysm will destroy Azeroth as we know it. Nothing will be the same. In WoW.com's Guide to Cataclysm you can find out everything you need to know about WoW's third expansion. From Goblins and Worgens to Mastery and Guild changes, it's all there for your cataclysmic enjoyment.