I've played since 2006, and I always end up coming back. Maybe not this time, but that is for a bunch of reasons.
I play with a group of RL friends who convinced me to roll on a PVP server a couple years ago during one of our play times (we all play for months then quit for months, but this is the fastest our entire group has unsubbed after an expansion). The thing that usually brought me back, was the leveling. It appeals to my OCD, and I can relax and get into it. Unfortunately they implemented CRZ which has drastically changed the playing on PVP realms. I leveled four characters on the PVP server prior to CRZ with only minimal issues (and most of those were the, rogue shoot bowing you, or the priest MCing you off a cliff; things so funny they couldn't make you angry). Now we're merged with all the other high-pop PVP servers, and any attempts I've made to quest have been met with utter failure at every level.
So now there isn't incentive for me to return and level, unless I want to return to my dead PVE server where my group no longer has interest playing (the only reason they stayed subbed for so long was throwing people off of the cliffs in Pandaria).
I found the questing in Pandaria to be awful. I had 14 85s, over two servers, just because I loved cataclysm leveling so much. I managed to get two characters to 90, and a third to 87, before I just couldn't handle it anymore. That isn't even factoring in the realization that for every character that hit max level it was the start of the daily train. I've never been good at, or enjoyed dailies. I am the poster child for casual playing. I don't need the fancy things, I just want to level, have fun with friends, and not have to feel like the game is a second job. I did my best, you know, tried to muscle through, but ultimately I failed and couldn't keep doing two hours of dailies every day.
I was really hoping pokemon would interest me, because I had nearly 200 pets before the patch even went live, but aside from seasonal pets I had all of the rare ones within the first week camping on two servers and abusing restarts, and the actual battling isn't really interesting to me at all, I never even unlocked the dailies. I'm not anticipating much of anything convincing me to come back. Especially once they activate CRZ in Pandaria. I just need to find a game that can fulfill my leveling enjoyment, that has good music (I totally play with game music on and am in love with it, entering Tanaris still makes me smile) and I would probably be free of WoW for good.
I would definitely, hands down, come back if the implemented a pay-per-minute sort of feature. Fifteen bucks just isn't worth it for me anymore when I only feel like playing a couple hours a week, or when I do play it's interrupted by PVP. If I could just pay for what I used in terms of logged in game time, I would be back within the month, no question about it.