The expansion looks great. Worgen alone is a good enough reason to play it.
I bailed a few years ago but will probably re-subscribe for Cataclysm. I like to keep my main at max level.
I started looking at the Blizzard forums again a few weeks ago for the first time in ages. Looks like the game has changed a lot. I had no idea what most of the people were talking about.
Because of that, I'll probably start a new character so I can learn what's new as I level up. Maybe roll a warrior. My main is a Rogue and I had a Pally in the 60's when I left.