Amazon sent out an email today to Cataclysm pre-order customers. The email claims that the game will be released on November 23rd.
MMO Champion claimed earlier this month that the release date is November 2nd. As they noted at the time, though, Blizzard could very well push this date back. Cataclysm is currently in closed beta while Patch 4.0, the update that paves the way for the expansion, is on the public test realm. The release date will perhaps come down to how smoothly the testing proceeds.
Update: Tip reached us from PTR that crit-cap, for tanks, needs more fine tuning. It seems Blizz still have a lot of catching up to do before releasing their next expansion 🙂