So far all of the Allied Races have been "subspecies" of the current races in WoW. Most of these have been minor reskins of existing races, which is fine since Allied Races were advertised more as unlockable cosmetics to add some NG+ value.
However, Vulpera seem to change that. They are an entirely new race added to the game, and the only thing they have in common with their counterpart race is that they are a small race. But Vulpera are in no way a subspecies or different tribe of goblin.
As the only completely new, unique race of BfA, this puts an imbalance between the Horde and Alliance. So, I'm thinking this implies that the last two AR reveals will include a completely new race for the Alliance side. This leads me to believe that Lightforged UD will be for the Horde (not Alliance as many were predicting), and the Worgen's counterpart race will be something completely new. Sethrak might be on the table but make little sense to me as Alliance has very limited interaction with them. Ankoan/Jinyu would probably make the most sense... but then again Gilgoblins didn't make the Horde cut.
At any rate, it seems the last AR for Alliance is still the biggest mystery of BfA.