It's hard to gauge the current subscriber status of WOW at the moment as Blizzard won't release their data. However, there is a website dedicated to tracking the subscriber population in WOW and that is warcraftrealms.com. With a dedicated band of volunteers, they take regular census snapshots of servers with a mod called "Warcraft CensusPlus UI mod". More info here:
http://www.warcraftrealms.com/censusfaq.php
One of the most useful parameters for measuring the health of WOW is "Weekly Activity". When WOW is expanding and attracting new subscribers, Weekly Activity goes up and when WOW is declining and losing subscribers, Weekly Activity goes down.
Below are graphs charting the Weekly Activity over a 12 month period:
Alliance:
Original:
http://www.warcraftrealms.com/weekly...-1&factionid=3
Image Snapshot:
http://img405.imageshack.us/img405/5...tyalliance.jpg
Horde:
Original:
http://www.warcraftrealms.com/weekly...-1&factionid=2
Image Snapshot:
http://img710.imageshack.us/img710/2...ivityhorde.jpg
The trends in the graphs match what I experienced in-game. At the end of WOTLK in December 2010, there was a sharp drop in player activities as people wait for the new expansion. When Cataclysm was first released, there was a huge spike in player activity as players returned. In the Weekly Activity graphs, this is exactly what happened in all Classes across both Alliance and Horde.
The most concerning trend is in January 2011. As you can see, there is a very sharp decline in Weekly Activity from late December 2010.
For a new expansion, this decline is very unusual. At this point in time, you would be expecting people to have already reached the level cap (level 85) and be working on the end game (i.e. heroics & raids). A declining trend probably indicates that people reached level 85 then stop playing; they are simply not doing heroics, raiding or end-game pvp.
Currently, there are plenty of complaints on the forums about heroics, raids, TB and class balance and the data presented seems to support that there are very significant players' grievances about Cataclysm.
The interesting part is how far this declining trend will go and when will it bottom out? Will the changes in upcoming patches affect this trend? How will new content patches affect it? The data will be most interesting in March and June when clearer pictures of player activity trends should emerge.
Without any official data from Blizzard, this is most objective data we can use. It's not perfectly accurate but it does provide a reliable measurement of the current state of the game. If this thread doesn't get locked or deleted, I'll be back in a couple of months to update this post.