Isn't the void threat the whole point of unification? There is a void invasion of Azeroth, Quel'thalas is the focus of the expansion, and the Sunwell is in need of protection. I wouldn't call that a case for Blood Elves to keep relations exactly the same. It is literally the catalyst for change, and directly implied to be the reason for unification.
You need to unite the splintered Elven tribes and defend the Sunwell. Yet you think the Blood Elves have no reason to want to work together.... Why?
Why are you ignoring the entire context of Midnight? You don't think there is enough concrete information, even though Blizzard implies Elven unification will be happening, and has given the motivating reasons why? Because we're not basing these speculation on 'current Blood Elf relations', they are all contextually specific to Midnight.
But even the Dark Ranger customizations are only canon to a certaib point. What is canon are the Dark Rangers returning to the fold. What isn't canonized is any other class combo for the Darkfallen skin; that remains to be addressed by lore. Like until we see Darkfallen Night Elf Druid NPCs or major characters presented in the game, I don't see those combos being canon. Same with Sand Trolls, I don't think there was lore for them at all.They are pressent on both factions, this was their solution. Its part as they called it, your inpretation matters and is canon. Same as how darkfallen work like san'layn
Wildhammer is supposedly canon, but I could never find the right source for it. I've only been taking people's word for it, since it seems collectively agreed upon even amongst lore buffs.