Everyone seems to safely agree WoW is just getting murdered in the eastern markets and that it will continue to lose subs there. It's likely that the Eastern market will continue to fall off rapidly. No one really cares because they believe NA market is fine.
Well, here's some fun math for you guys:
According to http://www.realmpop.com (Recording any toon that has ever posted to an auction house or been in a guild with any player who has ever posted to an auction house)
The current # of recorded lvl 90 characters on all NA realms is: 2,564,128
If we give an average of 3 level 90s per account (seems a fair number to compensate between those with 1 lvl90 character and those with 11 lvl90 characters), we reach: 854,709 accounts in North America.
Giving a lot of leeway in these results for instances of accounts that have zero level 90 characters and/or those accounts that don't meet the criteria for crawling (extremely rare), I think it's pretty safe to estimate total NA account holders below 1.5 million.
Doesn't seem so big anymore imo.