Speaking just of the U.S.:
There's an article from 2009
stating that 46 million people in the US play MMOs. Another article from 2011
puts this number at 39 million active U.S. MMO players.
It's currently estimated that there are 315 million people in the U.S. as of 2012. That's somewhere around 8-9% of people in the U.S. playing some form of MMO (F2P or otherwise). That's pretty impressive considering when you account for demographics and other limiations (gotta have internet, computers are not in every household, etc....). I expect that this percentage will grow over time now that mobile gaming has introduced millions of people to the concept of gaming with others online....and companies are following suit: just take a gander at Bungie's Destiny
Those are crazy numbers that can't possibly be accurate if counting just MMO's.
WoW peaked at something like 10 million world-wide and it probably has more subscribers than all other MMO's combined. The majority of those "subscriptions" are Asian market and not on the same level, dollar-wise, as Western accounts.
Last official word we had was TOR was sitting around 500k subscribers, and it was #2 in subscriber numbers.
So, unless there is some top secret MMO out there with 30 million secret subscribers, then those numbers are pure fantasy.