The guys over at The Instance podcast got a chance to talk to Blizzard's Tom Chilton about the recent decision to sell in-game noncombat pets for real money, and the interview is now up in the latest episode on their site. He talks first about the pets' development, and it sounds like they designed the pets thinking they'd be sold on a real-money store eventually. He says the price point was "arrived at by trying to figure out what it would have to be to make sense for us to spend time working on it." And he mentions the TCG and their loot prizes -- he says those were meant to be a bonus, and they ended up being a roundabout way for players to buy pets anyway, so Blizzard decided to go with this more direct plan.
He doesn't say much about the future, but he does say that Blizzard is planning on doing some "pet and plushie" deals, where you'll be able to buy a plushie from the Blizzard store, and get an in-game pet with it. For the game specifically, he mentions the guild transfer service that's coming (we heard about that back at BlizzCon -- you'll be able to server transfer an entire guild rather than do it account-by-account), but otherwise he tells players that the pet store is just a "side project" -- right now, it's not taking away from development at all, and if it does grow, Chilton says Blizzard would hire more people rather than using current developers. We'll have to see what happens in the future.