It may be popular. But in my limited sample of the world, on my server, there is a lot of frustration with the way the game is currently being developed.
Many of the long standing players I know quite frankly are already bored just months after the last expansion. Bored because in five years, Blizzard hasn't changed the formula of the game on bit. Bored and frustrated with the way Blizzard is managing changes to character classes.
Ultima Online, back in 1997, had more variety for game content and far less resources.
In addition, Blizzard appears to be getting quite a bit more touchy dealing with community feedback. Mass deletions of forum posts that are complaining about an issue might look good for forum maintenance, but it doesn't actually stop the bitching.
Maybe it's arrogance from their successes.. who knows. What I do know is that it's currently debatable whether many of the people I know will still be around when the Lich King content is introduced.
Frankly, I wouldn't be surprised to see a collapse in their subscribed base over the next year for Warcraft.