Existing lore is not a hinderance to new lore, and blizzard has even shown they'll happily retcon existing situations and lore to make way for new ones they wanna do, we should know this by now - ANYTHING can happen, espeically if it is something that helps cut development lines or makes the story juicier.
If I had argued in a forum post that they should destroy Teldrassil and move the story forward - you'd be replying saying Darnassus is racial captial, they would never do that and list lal the reasons why things have to be that way, but all of it means jack, when you progress a story or develop things, new things happen, and the motivations vary, whether it's practical, or gameplay, or cost effective or just lore.
The fact the very alliance elves are on the horde is one such example and you honestly think that Night elves can have Surmaar because it's horde. They could give Void Elves Silvermoon or destory it tomorrow. I'm sure a lot of blood elf fans don't want that.. do you think Night elf fans wanted their race genocided or their home destroyed?
Just because you don't want a thing to happen doesn't mean it won't, you should know this, you're not a child any longer you make do with what happens and in franchises like this you really are on for the ride, you don't determine anything in game. You should never consider any possibility as never going to happen, that's just begging for it to happen.
- - - Updated - - -
If you say, and if it makes you sleep better at night