Given that we know very little about them, apart from what they look like, it stands to reason that we also don't know quite where they come from. It should be noted, though that they're in the two colors that neatly align with those of the game's factions. Perhaps a clue?
This suggests that the mount is faction-specific, so, again purely speculating, this might indicate one of several sources. Faction-specific mounts could come from the battle.net store, where buying one item nets you two, such as existing pets. Or, it could be another, similar reward, such as the Spectral Gryphon or Spectral Wind Rider awarded for a successful Scroll of Resurrection. Failing that, and looking a little more on the bright side, it could be a reputation reward available in recolors for both factions. Or, we could be reading far too much into the color element!
MMO Champion has a video of the new mount in action. What is your take on it? If it was a pet store mount, would you buy it?