It was recently announced that the Guardian Cub will be placed in the Blizzard Archive in the near future. Once there, it will no longer be available from the Blizzard Store. [source]
In approximately two weeks (no sooner than June 18), the titanically cute Guardian Cub will vanish from the Battle.net Shop and head into hibernation in the Blizzard Archive. If you’ve been thinking about adopting this in-game pet, now’s your chance before it's no longer available for purchase.
The Guardian Cub is tradeable so players can always search for this pet on the Auction House. Do so at your own risk though, as in-game prices may shoot up once this pet disappears from the Blizzard Store.
Guardian Cub Retiring From Blizzard Store Soon
June 06, 2014