What if the reason why there isn't a new race is because...

[Averax]

Hybrid race options don't really make sense lore wise. Hybrids aren't impossible obviously (although some combinations probably are) but they are extremely rare, rare to the point that we've only met one after traveling all over Eorzea.
A thousand hybrids suddenly appearing in Limsa would be silly.

The warrior of light is treated as a solo entity, created by hydaelyn. This can mean whichever form she deems appropriate. This isn't like wow where a race needs a decently sized populus for them to be lore friendly

Adding a single new race with any significant variation from the existing races would essentially be an expansion in itself for the Art team because of the hundreds of gear items that would have to be updated to the new body shapes. This is why I am not expecting anything more than a new race with a tail / face / height changes in the future.

Not really true

All character models are based off the hyur male (it is used as a default), just proportioned and animated differently. Do the /flex emote, you get stuck in the hyur male default pose for a second no matter what race you are. That's why they don't have to re-adjust the gear on new races.