Sadly, Void Elves don’t feel all that much like High Elves. I say this as someone who got very excited back when they added Void Elves to the game.
Basically, there’s a reason players kept begging for years to get additional cosmetic options to make their Void Elves look more like High Elves. From the ability to hide tentacles, to having more regular hair and skin, and blue eyes. But a lot of players still feel that Blizzard didn’t do enough. Partly because the list of available hairstyles is still quite short, but also because you turn completely blue sometimes in combat.
In short, even if you sometimes look almost indistinguishable from a regular old High Elf of the Second War, you still don’t really feel like one.
This is a dividing topic though, because to a lot of players all of what I just wrote is complete nonsense, and what matters most to them is having fun and challenging raid content, cool encounters, etc. But to a significant section of the playerbase, the nuances of cosmetics and shaping your own character are very important.
As for High Elves being central to Midnight, I would have thought that was a given already? Chris Metzen’s pitch at BlizzCon was basically all about returning to the good olden days in Quel’thalas, where all the elves would be united against the darkness. I think as long as we also get some Forest Troll action, most people will be satisfied with this theme.