If the epic pet(s) are rewarded from Wrathion's quest chain, I will be VERY disappointed. I've had no desire to do the legendary quests this expansion, as I haven't found it to be very "legendary" at all. But that's a different discussion.
I'm probably 1 out of a hundred that didn't bother with the quests, though, so meh.
Anyway, if they add a pet reward to the end of that chain, that means I'm going to have to power through from start to finish, and pray I complete it before the end of MoP. Pretty frustrating. It'll make it pretty mandatory for collectors/battlers to do; what will happen to those that start collecting after MoP? Will they have a tough time completing the quests since there will be fewer people doing ToT and other raid instances?
This would make it troublesome for some players to get (after or even during this expansion), which would make it frustrating for battlers since an "epic" pet will probably be a MUST in their battling line up. By no means should the epic pet be "easy" to acquire, but since everyone will want/need one, wouldn't it make more sense to make it more widely available?