Ultimately it was only a matter of time. No MMO can maintain an upwards subscription rate forever, least of all one with as many subscribers as WoW.
No matter what they do to the game, they will ultimately lose subscribers. It's just a matter of which ones they lose first.
MMOs all have a "Best By:" date printed on them. Eventually you reach a point where people begin to leave faster than new folks become interested, either because the game has changed too much, or because it hasn't changed enough.
Blizzard knows this on some level, and that's why they are going to try and focus on Titan. At this point they have zero incentive to change their approach to WoW. They know that no matter what direction they go, they'll run customers off.