MMO-Champion has a screenshot of a datamined model from the latest beta build. The colors are STUNNING! I hope they'll all be available at some point or other.
I don't know about everyone else, but it's cute enough to be a pet to me - possibly the MoP CE pet? Or it could be the new guild rewarded vendor pet, the Thundering Cloud Serpent Hatchling!
Although the model seems a bit reused I'm loving the colors of these baby serpent hatchlings, and who could say no to those big round eyes? I hope they have some neat idle animation or companion/environmental interaction. If this is the intended Thundering Cloud Serpent Hatchling pet, how cool would it be for it to suddenly have a lightning aura during a rain/thunder storm? :D