It was a really high probability. The lore rationale based on the provision of golden eyes seemed strong. Unfortunately it turned out those of us who wanted blue eyes on Blood Elves were mistaken, and that is disappointing. The flaw with your response and apparent delight that we were proven wrong is that you refuse to extrapolate the rationale from why we didn't get blue eyes to your own request for high elf like customisations on Void Elves.
Blood Elves didn't get blue eyes because, according to the devs, they have moved past blue eyes. Similarly, Void Elves have 'moved past' being high elves, and their skin tone range exemplifies that aesthetic. Your own avatar highlights the contrast they are going for with Blood Elves and Void Elves, between the light and the dark, the contrast which they emphasised with Blood Elves getting golden eyes.
If they were reticent to grant Blood Elves something as small as a blue eyed option for reasons of lore then the chances of them obliterating the very aesthetic basis for the void elves through normal skin tones options cannot be viewed as anywhere near likely.
As for the supposed negativity, the request for high elves undermines faction integrity and has more than a whiff of sour grapes about it, with constant references to the Alliance being screwed or not getting what they wanted, with no appreciation given to the reasons WHY the Alliance didn't get exactly what was wanted. The saltiness among some regarding their faction is to be pitied. If they have such a problem enjoying that faction, perhaps they are on the wrong faction.
But they shouldn't be seeking to undermine one of the unique aspects of the Horde simply because they are unhappy with the status quo. Hundreds of different races in the game, hundreds of possibilities, and the one they keep complaining about is the Horde's most popular option.
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No they wouldn't. This population balance thing is such a red herring. It is completely immaterial to the debate.
The fact you even cite High Elves as a fix proves my previous point, hundreds of ways to fix possible issues and all that can be thought about is copying the Horde's most popular race.
The population imbalance is due to the stronger raiding community within the Horde. People were drawn in by stronger racials. Now that the community is old and well established they don't wish to move, even as new Alliance races have gotten stronger racials, because it is access to people that matters, not what race they are playing.
If the Alliance got high elves you'd probably see a small change in the balance but it wouldn't fix Alliance raiding or Alliance feelings of inferiority. Void Elves didn't do it and for the vast majority of people the model that is indisputably an elf was enough (given they are already the fourth most popular alliance race).
Somehow I doubt a single skin tone is going to fix all the woes the Alliance playerbase seems to feel it has.
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But there were signs of them in the datamining of 7.3 when the bones of the Allied race system were put in place. That is where we are now in relations to Shadowlands, with character customisations being datamined and none of the outliers that could hint at Void Elves getting to look like high elves being found. None of the core races are getting them, so clearly you have to be hoping the Allied races get 'special' treatment.
Like green skinned Mag'har Orcs. Should we expect those too?
There is even strong lore behind it. Some Mag'har fell into some fel. Ta-daa! Completely undeniable, water tight logic as to why a Mag'har Orc should have green tones. And if you dispute it you clearly just don't have enough vision.
Or what about non-mech customisation options for Mecha-Gnomes so they can look like their leader, King Mekkatorque? Besides a fetching chest piece he doesn't have any mechanised bits at all. Should THAT be an option too? You can say that they found their removed arms and legs and reattached them.