Ummmm... yeah... yeah they actually do quit.
This is why Cataclysm (and all of MoP) had a massive shift in game design philosophy mid-way into the expansion. You don't just do that kind of a shift overnight, especially after GC posting a "Players need to stop complaining about difficulty and just step it up" speech 2 months prior.
We'll really know what's going on next quarter, a quarter that does NOT end on the same week as an expansion launch. :P