Both yes and no. I'm looking forward to MoP due to me being bored out of my mind with Cataclysm at the moment, and wanting to see how the new changes play out. However at the same time I don't like the new talents at all, and find most of them quite useless as a tank - I'm not that fond of Blizzard giving us even less talents to pick from, making things even simpler.
I will still play my pally though, but if things are really bad and I won't like playing my paladin as my main anymore, then this might be the expansion that'll stop me playing WoW.