Obviously, there’s no word about how you’ll get this pet, nor are there even screenshots of what it will look like. It could be a cross-promotion between the games (which seems likely as the model is encrypted), or it could be a major reward from the next expansion. But it’s in the game’s files, meaning that at least some work has been done on it. Good news for everyone whose pet collection doesn’t include enough turtles at this point.
World of Warcraft and Hearthstone ostensibly take place in the same world, the latter frequently gets to fill out the lore of the former. In Hearthstone, for example, you get extrapolations on ideas like Gadgetzan being an actual city, or you get the Tortollan being added to the world’s lore. They’re a diminutive race of turtle-people not seen in the MMO… at least, not seen there before now, judging by the Tortollan pet that’s been datamined in the game.