Of course. If the developers change their mind they can easily make Alliance High Elves possible. But I think anyone who starts arguing that Blizzard can retcon the current situation is implicitly accepting the reality of the current situation regarding the exiles and their status.
Your second point is the slippery slope though and yet more proof that there is no unified pro High elf demand.
Some reject the idea of void elf customisation outright, only a pure High Elf option will do.
Others will accept void elf customisation.
But there are other for whom void elf customisation wouldn't be enough and would want updated racials. And maybe emotes. And the Paladin class wouldn't go amiss either.
There are levels of what is apparently acceptable and each individual differs on what they would accept.
Frankly I think what is likeliest to happen is that they'll give Void Elf players a monkey paw result. Normalish yet obviously void flawed skin tones that still drive home the message you are playing a Void Elf. I think they would be very, very wary of attempting to facilitate the 'de-voiding' of Void Elves as that is the core theme of the race. Think of their actions during the character model updates, they set out to rebuild the models but they also kept them spiritually in tune with what went before. Their philosophy was that someone playing a particular race clearly enjoyed that model, and that they were the people they had to please, not groups who hated the model and wanted Blizzard to transform it into something else they would prefer. The same philosophy should be presumed to be at work here and that whatever customisations void elves get, the won't violate or compromise the fantasy of being a void elf.
Because ultimately, just as there is a werewolf option in the game and nobody questions that despite it being Alliance only, there is a traditional style high elf option in the game and if people want to play that, well, the Horde IS waiting for them. Just as it would be unfair on Blood Elves to duplicate them to the Alliance, it is unfair on Void Elves to devalue their own fantasy and attempt to turn them into ersatz high elves.
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Not at all, I am critiquing the comparison. The notion that Blizzard reversing course on classic servers presages a similar about turn on Alliance high elves has always been one of the sillier things blurted out by the pro high elf movement. That was a juggernaut of a movement that few other questions in WoW's history have ever replicated. The closest I can think of was the flying debacle of WOD where there was an outcry, and they did change (but not reverse course).
As for Blizzard changing their minds, well, we don't know if they will change their minds but it's not as if we have no evidence of which way they are leaning. Fifteen years of commentary can all be summed up in one message. Blood Elves are playable as the high elf option of WoW. If you want to play a high elf, the Horde is waiting for you. If you can't stomach the Horde, the high elf variant of void elves is a part of the Alliance.