Pretty much we can expect the last 2 ARs on 8.3.5 along side the Troll Heritage and the Draenei one.
Now i like the idea of Ogres, sethraks and Vrykuls.... BUT! i can recall hearing, idk if it was on an interview that they asked about allied races and this races are considerate as Creep Races, (True Neutral) as these ones cant server the Horde or the Alliance at its full, meaning they cant be part of the Factions and Factions are the pillars the Warcraft franchise. And yes, i am aware about Horde Ogres on dustwallow marsh, hek we even got new Ogres from the AU Draenor scenario.
Now there are other races that not only can be playable because of new models, but also can help expand on plotlines or becoming plotholes in the future, just like:
-Moknathal> New Rexxar Model and Outland plothole and new Wc3 reforge models for Beastmasters. Could go for Horde
-Saberon> AU Draenor survivors that traveled with the Horde champion, could go Horde or ALliance
-Humanoid Evolved Botani> AU Draenor survivors that traveled with the Horde champion, have affinity with Nature, druidism, Freeya and Eonar. could go for Alliance.
-Redeemed Undeads> Seeking redemption with the True Heir of the Lordaeron Throne, could go for Alliance.
-Thin Humans> Much likely to become a character customization, but the first Thin HUmans were the Defias Shadowguard as Proto alpha Humans for WoW. So much more related to Assassins styles, could be something like an Alteracian version, who knows.
-Ankoan warriors> Really different for the Gilgoblin versions on nazjatar, these ones are New HD version of the old Jinyu Fish people, with a better "skin integration" to gearpieces.
If i should bet, i would go for:
Moknathal Horde
Redeem Undead Alliance
Why? because of how Moknathal got the "new race treatment" not only with Rexxar on WoW (wich model can be literally hide the headpiece) they also got the remodeled on Warcraft 3 reforge.
And Forsaken HOrde Undead are going to get new "no exposed bones" versions on Shadowlands, meaning that "no bone" holy infused versions could happen too.