So, realistically and logically....

[Lihtleita]

Yoshi has literally explained exactly why they chose to do this though.

They wanted to add in a more bestial race like the Ronso, but felt they had to put the Viera in because it was the most demanded race.

in another timeline we got a bestial viera race w two genders

[Seraphor]

in another timeline we got a bestial viera race w two genders

Pleasing even less people...
"These aren't real Viera!"
"I wanted to play a Ronso not a giant rabbit!"

[Halivel]

Pleasing even less people...
"These aren't real Viera!"
"I wanted to play a Ronso not a giant rabbit!"

Hard to say. There were not any hints about Ronsos so people where actually susprised. And because they promised back in 1.0 to not repeat gender-lock, a lot of those, who asked for Vieras, actually really waited to see males as well.
Still, with what you are really right, in case if they would add one full race, there is almost a zero chance to see another one in future. So with creating this situation they kept a big window for themself. Not to mention that optimizing armor for missing genders will be easier when they know already how to do it based on expirience with female Vieras and male Hrothgars (because their counterparts likely will be similar to them in proportions). And Yoshida sounded in his interviews like they want to complete them, just can't promise anything right now because of resources.