Hellfire Citadel, Tanaan Jungle, Timewalking dungeons, and shipyards are headed to World of Warcraft on June 23 with patch 6.2: Fury of Hellfire.
I'm on record, when we saw the introduction of pet battles, as saying 'Well, this isn't content I care about, but it's good for people who like it' because pet battles are utterly optional. The various rewards you get for pet battles only affect the pet battle minigame itself - stones and other rewards that affect the pets and how they level. There's never a reason to play pet battles if you don't enjoy the gameplay - you're never forced to do it, nor do you even feel forced to. I can say this having utterly ignored pet battles since their introduction.