Stropp's got an interesting piece of speculation that says though "Cataclysm" is still probably the next expansion, the event the word refers to has yet to happen. He claims that if Blizzard really wants to speed up the 1-50 leveling process, they should just destroy Old Azeroth as we know it, and just have all the new characters start at level 50. That would be pretty nuts, but then again, Blizzard's never shown a real affinity for the old content, and by the next expansion, we'll be heading up to level 90 or even 100.
Finally, there's this: when the news first broke last week, we noticed that the wowcataclysm.com domain had just lapsed when the trademark was registered. But apparently, as a few of our commenters have noticed, the Australian person who originally owned it has re-acquired it for another year. So if "Cataclysm" really is the next expansion, Blizzard will have to lay claim to the domain (either by buying it or trying to enforce their trademark), or (more likely) put the domain somewhere else.