Well, WotLK will clearly be more of the same, so you have to ask how much you like the current product and how badly you wish that there were more of it.
But really, here's the thing. MMOs aren't hard games. They're usually not very strategy-heavy. They're pretty simple. The reason for this is that, in order for a modern MMO to break even, it has to have hundreds of thousands of subscribers, which means that it has to have very broad appeal and be easy to pick up. It also has to be addictive. In fact, if you consider the two ideas of "fun" and "addictive", I'd say any MMO dev worth his salt would pick addictive first, fun second if they have time for it. Why? Because people have to keep playing it for years or the game will never turn any profit.
Because of this, and the fact that there are a few ways psychology notes as the "best" ways to addict people, many MMOs follow a very standard formula, and the only real difference is in the window-dressing, fine detail, and population. That's why I don't understand why fantasy MMOs keep being made. What we need to realize is that WoW is not the current champion, or anything like that. WoW has won. Period. For fantasy MMOs, WoW is the winner. It has the population to keep new players stimulated, and enough success to churn out regular and often not game-breaking updates. Why would I play a different fantasy MMO with less people to team with, a smaller dev staff, and less regular content? You fight dragons either way.
What I'd like to see is more MMO genres, more superhero, sci-fi, maybe WoD even (my personal hope). Sure, it'd be a smaller subscriber base, but I might jump in there just because I'm sick of looking at elves.
So sure, check out Warhammer, but don't expect anything earth-shaking from it.
- J