Well I wouldn't complain if it was a Blood Elf option, I am speaking strictly lore wise as Forsaken with Sylvanas and Dark Rangers has been like the picture of undead High Elves.
If it was a Tauren option I wouldn't complain either just to be hyperbolic to show if it happen, I wouldn't mind
how it was done if you know what I mean(because I really, really want it), but my point is how I would have done it if Undead High Elves had been a thing. About the rest of your post which is logical for sure, personally I think the chance of it to happen is rather slim(and I fear the chance is less than that), because I think the devs are quite happy now with how many races we have and such, but the possibility is always there, and quite frankly that's always a positive thought. Which is why I added maybe in two years in the latest post, because that's how I like to approach this
That little chance is the reason why I am still hoping for it, and we'll never know!