In fact, with all of the upcoming tameable Wrath pets, not to mention exotics, the stable situation is looking pretty painful. In a recent forum thread, Ghostcrawler hints that Wrath might bring additional slots, going against what Blizzard has said in the past.
As a response to posters asking for an expanded stable, the CM responds with "okay."
I can't express how excited I am about the possibility of one or more stable slots. Could this tie into the Achievement system? Will I be allowed to collect and house pets? Will we see a special "exotic" slot or slots? What do you think?
Update: Ghostcrawler has confirmed that we will indeed be getting two new stable slots. In fact, Ghost points out that further testing may lead to the stables being integrated into the UI the way non-combat pets and mounts will be. In other words, summoning all pets would become spells, allowing the hunter to call whichever pet he or she wishes, without visiting a stable.