The Escapist spoke with WoW Production Director J. Allen Brack at BlizzCon '09 and asked him the million dollar question: How did the WoW team react to the Cataclysm leak? Here's the answer:
"They went through the five stages of grief, really [denial, anger, bargaining, depression, acceptance]. It's hard to not have this initial irritation, where you work on something, you want to build up a surprise, an awesome reveal, and have it yanked out from under you." But as the weekend went on, and they saw how the WoW community was getting excited about the news, it became easier to accept. "The reality is, the fans still went crazy for Cataclysm."
All's well that ends well.