We know it isn't the new moogle mount (That was already shown).
We know it isn't the new primal mount, or a achievement mount related to the primals (Not enough primals out in the series as someone else said).
We know it's probably not the PVP mount in a "spiritual" sense (Unless you can kill you friends by dropping them off Sparta style at high distance).
The odds of it being a new recruit a friend or veteran reward seem kind of slim.

I think we all know the only question remaining is how much it costs... (unless there is something we are forgetting).