This was taken from the Blizzard Twitter Q&A today:

Q. Will there be any new pet families added, or will we simply see more additions to existing ones?
A. We’re not sure yet whether we’re adding new pet families or not. It’s possible. Expect to see some monkeys, foxes and other new pet possibilities though!

Pet foxes! How neat!! Rosco could be joining me in WoW. I hope Kiba doesn’t get too jealous.