My thoughts are simple.
War Within would’ve been a great time to give the Dwarves some Earthen customizations, the Trolls some Proto-Troll customizations, and introduce the Sethrak as an Allied Race (neutral even makes sense for them to a degree).
Midnight would be a great time to add Ethereals as an Allied Race, but if they added Earthen to TWW, then it’ll probably be High Elves for Midnight. Speaking as someone who has wanted High Elves as a playable race… it’d be a bad idea. Midnight taking place in Quel’Thalas means it should 99.99% be devoted exclusively to the Blood Elf narrative, which has survived off of breadcrumbs since BC. I’ll also reiterate what I’ve said before, but one of the key defining narratives for High Elves in the setting, was putting Quel’Thalas below something else on their list of priorities. Old Alliances, family, mana veganism, whatever, for the High Elves, Quel’Thalas was not #1. Giving them any kind of presence in Midnight in Quel’Thalas is going to feel like a step backwards in their narrative.