Blizzard will set this change in motion on the Beta first, and if everything goes smoothly it'll go live (no word if it will happen in Wrath of the Lich King or patch 3.0.2).
Kaplan notes that with this change Collector's Edition pets will no longer disappear when you put them into your pet spell book. The spell will still be added, but you will be able to send the pet item around to your other characters on your account.
He does point out that if you've already put your pet into the pet spell book, you won't be able to be refunded the pet on the beta. Of course, that does not apply to the live realms – since the pet spell book isn't implemented in live.
Update: A few people have asked if you can have the Panda, Zergling, and Diablo all on one character. The answer, according to Kaplan, is yes.