I have no real doubt that the PHB we actually get will contain multiple elves. I'd rather it didn't, but the designers' ongoing fetish for elf-love remains strong.
Heh, this thread welcomes the way 5e now treats subraces as separate races. I feel this is important, so each race concept can be fully described narratively and mechanically without being constrained by base race requirements. For example, it annoys me if every elf must have darkvision, even when it makes less sense. Separate races is a way to format a family of related races.
However. The call for there to only be ONE kind elf without any variants, convinced me pretty much immediately. If the elf player can choose the cantrip, and spell, and background feat, there doesnt need to be any other races, mechanically. Let eladrin cultures tend toward certain cantrips and spells, and drow cultures tend toward other cantrips and spells. Same mechanics. Player chooses. Setting recommends but doesnt require.
On retrospect, the elf does need two separate races. But both of them need to be called an "elf" or elf fans will cry if their favorite version doesnt get the name elf. Heh, I know I would.
Lets call them "sun elf" and "moon elf". The sun elf is the same thing as the astral elf, mechanically. The astral elf is well thought out, and its trancing is flavorful with useful proficiency swaps. It has the Misty Step teleportation per proficiency times per day. The teleport is highly useful in my experience, for any chosen class. (Might as well rename the spell itself "Elf Step".) Instead of a preassigned cantrip, let the player choose any cantrip from any spell list, so the race mechanics can be more useful for more elf cultures. Finally, instead of "sunny darkvision", choose any level 1 spell and cast it for free per day. So, elf races that cast innate spells, can use this race instead.
The moon elf is culturally nocturnal, but enjoys the twilights after sunset and before sunrise. It has darkvision and the twilights appear glorious because of this darkvision. Where the sun elf has Misty Step, the moon elf has the precisely agile Elven Accuracy. It shares the same trancing including proficiency swaps, and choice of cantrip for innate magic. But the moon elf is quick improving speed instead of gaining a spell.
The moon elf can handle most of the standard elf subraces, including wood, high, and uda-drow, plus FR moon, 3e wild, 1e grugach, 2e-4e athas, and others.
The sun elf can handle most of the exotic elf subraces, including astral, eladrin, 1e grey and faerie, 2e-3e-4e FR sun, Wildemount pale, and probably aeven-drow, and maybe loren-drow.
Change Darkvision and Waterbreathing into cantrips that any caster can choose. So a "moon elf" that takes Waterbreathing is defacto a "sea elf". A "sun elf" who takes Waterbreathing might be a nixie. A "sun elf" that takes Darkvision might be an aeven-drow or a shadar-kai.
A background feat can supply the uda-drow culture the Lolth spell traditions, like Faerie Fire and Darkness. Same goes for other backgrounds for other elf cultures.
Besides the two different elf mechanics, one for "sun" and one for "moon", all of the different kinds of elves are strictly cultures. Heh, two elf mechanics to rule them all.
The physical appearance of any elf can be whatever a player wants. It is already D&D canon that pale even whitish drow exist, and likewise dark even blackish astral elves exist. A player can choose any appearance, especially any reallife human characteristic.
Two elf races is actually enough for all of the 100+ elves in D&D traditions.
In the default lore, the astral elves, a kind of sun elf, are the original elves that reproduced from the blood of Corellon while in the astral dominion. The drow elves, a kind of moon elf, are the original material elves, who materialized into the material plane becoming creatures of flesh and blood. In the aftermath of their schism, the elves scattered across the multiverse, including elves of fey and shadow. Other elves of flesh and blood, including wood elves and high elves, are also kinds of moon elf.
However, one thing I am sure of is that the split between aevendrow, lorendrow and udadrow must be a matter of culture, and not one of subrace - it's problematic to have an all-evil subrace of elves, and splitting that subrace into three doesn't actually fix anything if one of them remains all-evil.
(Actually, I'd like the split between aevendrow, lorendrow and udadrow consigned to the fire, never to be seen again. And whoever came up with those awful names should be banned from using language ever again, as a lesson to others. But that's a whole other rant.)
I am comfortable with uda, aeven, and loren, being different but related elven ethnicities. Same goes for wood elf and high elf as ethnicities. I view the high elf as admixing the eladrin fey spirits. The 1e Greyhawk grey elves are eladrin who choose to materialize, while the faerie are the ones that remain in the feywild.
Two elf races represents everything well enough.
I hope, in 2024, we only see two kinds of elven races mechanics.
Anything else is a cultural background.
The only heritage missing from your list is Planetouched.
