The publishers of the game, Blizzard said that the numbers are down by 600,000 players in the last seven months. Blizzard reported another loss in the second quarter. Subtracting another 300,000 players from the game. This means that WoW has lost nearly a million users in about nine months. The reason that the decline might have slowed by Blizzard bringing in a free-to-play model. Players can play for an unlimited amount of time for free until a character hits level 20. Then they have to start paying the monthly fee for online access.
Blizzard has been releasing recent expansion packs like Cataclysm and future content like the Mists Of Pandaria. But it is starting look like the rot has set in and WoW is fading.
More here.