Which villainous race(s) are next on the chopping block?

[Morty]

Hopefully, all of them.

The goalpost has never moved. It has always remained: "If it is a sentient race, it has the capacity for good and evil and everything inbetween." WotC has just taken their sweet time inching towards it.

That's about the size of it. This isn't a complicated question and other games, books and stories of all kinds have managed to exist without universally evil sapient species. But it's treated as some kind of inviolate institution in D&D. I ran a Dungeon World campaign (which would have worked just as well in D&D if I was willing to run it) where there were no "evil species" and it somehow worked without a hitch.