Yep, World of Warcraft subscription numbers are declining for the first time in it's history.
In december 2008 WoW had 11,5m active subscribers, in may 2009 it was already clear WoW was stagnating with 11,6m active subscribers and now Blizzard Top Dog, Mike Morhaime, says WoW is stable with 11,5m active subscribers, which is actually a small decline of 100k subs.
However, meanwhile the GAPP ( Chinese government ) finally approved The Burning Crusade, so WoW China is back on track, and will probably bolster Chinese WoW numbers in the near future.
Add to that the upcomming expansion Cataclysm in the West and one can see that WoW still has a strong future ahead.
It seems WoW has actually been on 12 million players around January 2010, this means that their current numbers are a bigger drop than first assumed.
You can check this link : WoW and Vivendi at Reuters
At first I was reluctant to use this number, but after comparing them to the PCU numbers I got it looks to be valid after all.