I wouldn't worry about it, without China blizzard would only have 4.2 million subs. Still a large number compared to other MMOs but it does narrow the gap by a lot. Also I expect MoP to bleed a lot more subs over the course of the expansion, not because of any other games but because it's lost it purpose and journey.
The dev responsible for putting journey into wow is now dev lead for project titan, Jeff Kaplan. That will be the next time I pay for a blizzard sub again but for all we know it could be B2P with a cash shop.