Like a lot of old vets to WoW I am missing that feeling I had when first stepping into Azeroth, I miss my first instance run, my first guild, the first time I ever fought another player in Southshore. There are simply no more "big" firsts to do. Sure there's new content but it's not the same.
I want those firsts back and let's face it, Cataclysm cannot deliver that, but they sure can deliver a lot of new firsts, more so than any other expansion. My first worgen in a strange new land, filled with new leaders, new imagery, a new feel, darker undertones and most importantly bringing the war back to World of Warcraft. Enough of this tenuous truce between Horde and Alliance, I want war and King Varian is going to deliver!
On that theme, the thing I anticipate most is rated battlegrounds. This is like a dream come true to any fan of pvp. One of the things that Burning Crusade delivered was a revolutionary, albeit controversial, change to pvp via arenas... Cataclysm is now carrying this one step further and bringing the best thing about Vanilla pvp (battlegrounds) and seamlessly joining it together with the best thing from BC pvp (arenas).
I have a lot of faith put in this expansion, there are a lot of us old timers that need a new challenge, and I don't think we'll be disappointed.