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

[Theodric]

2.0:
-Sudden influx a Miqo'te men
-Sudden influx of Highlander women
-Sudden influx of Roegadyn wom-...oh nvm that

3.0:
-Sudden infestation of Au Ra, a race never known to exist.

The developers simply realised what a terrible concept gender locked races were. Furthermore all of the original races were already well established within the setting. Au Ra weren't but at least they came from Othard - somewhere we haven't seen in-game yet. With that said, though, they ended up being less 'bestial' and more like the other existing races. Which led to many people finding them to be rather lacklustre.

That doesn't really change the simple fact that half-elves have already been established as rare and heavily shunned. Elezen exist, Hyur exist - just expand the options available for both races instead of wasting development time on what will essentially just be a Midlander model with Elezen ears stuck onto it.

Thankfully this setting takes itself seriously enough that dumb combinations like Roegadyn/Lalafell hybrids won't likely ever be a thing either.

Maybe in 5.0 we'll get a new race. Who knows? It's not a priority when the existing races are in dire need of additional customisation options and representation.

[Magic-Mal]

That doesn't really change the simple fact that half-elves have already been established as rare and heavily shunned.

In Ishgardian society.

What about.. any other society? We already know Ishgard isn't terribly open-minded besides Aymeric lol.

None of which are incredibly rare, unlike half breeds, and in particular half-elves.

Thats not the point I was making. They are as rare as everything else in this game that suddenly appears.

Roegadyn children are nonexistent. Female Miqo'te children were nonexistent until recently. Male Miqo'te children are nonexistent. Au Ra children are nonexistent. Au Ra in general were nonexistent until SE created lore. Male Miqo'te were very rarely seen as NPCs in story until after 2.0(so 2.1 and up).

Au Ra have no background. No settlements. No nothing. They are just people that are in the world and the only explanation is "They're from Doma".

SE can EASILY make a new race. Just like Au Ra, Yoshi can easily announce to us

"Oh yeah, guys. I forgot to tell you. There's actually an entire continent that has an entire race of rabbit-like people and this city in particular actually knew about them the whole time and now they're all over the place in Eorzea but do not fear! As Eorzea as a whole doesn't care at all and only that city in particular acknowledges they exist within certain side quests that don't connect to the main story so you can play without anyone ever questioning what the heck you are."

That is Au Ra