Or, first thought. Singular.
This reminds me very much of Wrath of the Lich King, in that the content seems incredibly polished, and cohesive. The game systems are getting shaken up, and tons of new systems are being added (New Class, Talent changes, Challenge modes, PVE scenarios, Pet Battle System).
So, perhaps Cataclysm was a nadir… and now the only way to go is up. And that is a very good thing indeed. Mists will be an ambitious expansion, and it looks promising!