In the player garrisons coming in Warlords of Draenor, one of the medium-size construction options is the Pet Stable. While we were all initially uncertain as to its purpose, more has since been revealed. Below is an explanation from Cory Stockton's Twitter account.
.@perksnpeeves@gloriaboboria current plan is you can merge two pets of the same family and pick the breed. Doing this gives chance at epic.