While I definitely agree that Shadar-kai are not elves and should not be retconned as such, I actually hope the response to this UA is simply negative across the board. In a thread posted by Yaarel, they tally up that there will now be 12 variants of elves in the game with this UA, and that is insanely stupid. Not only because it has never been explained why elves sleep on a purple rock or something and spontaneously have an all new subspecies, but because this is a ton of work being devoted to a fantasy race that already has titanic presence in the hobby and culture at large. Why do we need so many damn elves, but no more human variants? No orcs/half-orc variants? Maybe a clan of dwarves that are a little outside the norm? There are so many other races that could badly use either more attention or simply introduction into the current edition that I can't help but be soured at more swipes at a low-hanging fruit that we have more than enough of already.