Blizzard just announced the next WOW expansion - the continent of Pandaria, containing the Pandarens, which are of course Pandas. Honestly they could have been just a *tad* more original in their naming schemes. Much of the internet is convinced that this is a sign of the apocalypse and Blizzard has decided to finally throw in the towel on 'real gaming' and just pander to the 12 year olds who want to play a Kung Fu Panda. Those people can safely be dismissed as bittervets. WOW has always pandered to 12 year olds, this is nothing new. Us old folk can recall quest chains revolving around collecting animal poop from every expansion, often several times an expansion even. Nothing has changed: Dwarf quests are still all about getting drunk, elves are still designed to be masturbatory fantasies for tweens, goblins are still futuristic mad scientists and undead are icky.
Whether or not the very noticeable decline in WOW subscriptions is reversed or halted in Mists of Pandaria is not going to rest on whether the jokes are sophisticated or not as that is already decided. I also doubt the trend will be significantly affected by endgame raiding balance. WOW was plenty popular back when balance was a joke and the really fine adjustments they make these days aren't even particularly relevant to the vast majority of the playerbase. There is a large pool of people out there who raid a little and a small pool who raid a lot and only the really hardcore players are affected by one class being 5% better than another.
What *will* determine the sub rate in WOW is how the casual experience changes. Right now the questing experience has a big story to tell, has plenty to do and is utterly trivial. Levelling in WOW was never hard but these days there is simply nothing you can do to get yourself killed aside from literally going afk and that I think is a bad thing. I also feel like the dungeon experience both during levelling and at endgame isn't working out well with the current Cataclysm design. Dungeons are just as trivial as soloing and there is no strategy, thought or feeling of accomplishment in beating a dungeon. Generally nobody even knows what abilities the monsters have because it simply doesn't matter. When a player arrives at endgame they are suddenly faced with normal dungeons that reward absolutely rubbish gear (compared to rep gear, Justice Point gear, etc.) and to kill things that drop loot you want requires a totally new skill set - heroic dungeons will kill you if you don't get out of the fire.
Cataclysm quests were much better than previous quests at providing 'raid training' to players and there were actual solo bossfights that I really liked. However, the contrast between the 1- 80 game and the 81+ game is far too stark. If Blizzard really wants to improve the game I think they need to take a lot of the quests off the rails and let people do them in whatever order they want and turn up the challenge on soloing and dungeons. Whether or not that stuff is going to happen in Mists of Pandaria is entirely unclear at this point, and although the new Monk class and Pandaren race are fine additions they don't say anything about how WOW will fare going forward.