Racist tropes WotC do not want to deal with can be combatted by just getting rid of half-species. All they have to do is say species can't intermix. It is fantasy. These are different species, not the same species with varying degrees of skin tones. We are discussing something that has a lifespan of 1,000 years versus something that only lives 60 years.
I, am by NO means, saying this is the best option. But, it is one of the easiest they could implement. (See my previous posts regarding how people love to play characters that are not accepted by either world they belong to.)
First, once they make it a precedent that species can't procreate, then they wait five years, and none of the new players will even think about it. If they make D&D more online friendly, then that makes it even easier to simply have an avatar.
It's not and I didn't say it was. I said, the easiest way for WotC to not have to worry about it is to the great handwave. Once they eliminate any half, then it becomes a game of tabaxi, lizardfolk, elves, dwarves, dragonborn, tieflings, and humans. They can have all the mixed humans they want, because mechanically, it won't make a difference.
This. I am just merely postulating that this is the easiest path they have.
I would say no.
If combinations are popular though, would it also work to say that "What some might erroneously describe as apparent cross-species found in published D&D books (centaurs, Dragonborn, etc...) or only imagined (dwarf-elves, human-orcs, Thri-kreen-dragon-born etc...) are separate species that arose in the ancient past - perhaps naturally, supernaturally, from other planes, or by magic (just like all the ones in the PhB). Rules for constructing balanced abilities for such people to be used as PCs are in the DMG. It also contains examples of how these peoples have unique names not based on their appearances. "