Blizzard has added the proto-drake mount that likely drops from Mythic Raszageth to the Mount Journal in the latest Dragonflight Alpha build.
The mount has a placeholder name [PH] Wind Proto-Drake with the “[PH] wheeeeeee wind!” flavor text and most likely comes from the Vault of the Incarnates raid because it has the same model as the final boss.
Here’s a preview of the mount from all angles.