In the latest producer letter, Naoki Yoshida set about answering the many alpha questions that have been pouring into Square Enix. (Sorry, but you'll have to wait for the launch to find out about Bahamut and Louisoix!) Yoshida explained why more testers aren't necessary, emphasizing that the alpha is currently locked at level 20 and focuses on simulating stress conditions for the lower-level areas.
Folks still hoping to participate in the alpha might get invites for the fourth phase which will start December 3rd and go through mid-month. Additionally, a third testing world will be opened at this time to allow for even more testers than originally planned. For more details, check out the producers letter.