Huh?
I don't know if Ereder deserve a spot, but Gilgoblins are pretty much set up with them getting a female model and moving to Durotar. Mogu have been hinted by a blizz dev and I feel like there are plans for Saberon (since they came to Azeroth).
What dev said that?They might add Tinker or Dark Ranger as classes with new customization but they won't market them as "hero classes" after the level revamp. And hell, even the Devs have repeatedly said a Dark Ranger is just an Undead elven hunter. And they've been in the "forsaken" even before the Human Forsaken. Seems like they're prime Allied Race real estate.
What cutscene?They're definitely going to add one or the other eventually. But I'm pointing out there's a lot of kinds of undead elf & they've been in the horde a long time AND there's an cutscene in game that feels like an undead elf allied race related, far more than anything like that for the Venthyr.