Faolyn
(she/her)
It could really easily become a setting, with all sorts of primordial-type stuff in it, neolithic races, the original great cities of the early elves/giants/dragons/whatever, Great Old Ones, and ancestor species that no longer exist.Not really, no, since thr First World as a concept is a couple of sentences thst provide a fig leaf to conformity between official D&D Settings and homebrew. It isn't a "Setting."
And it has a very easy out: at some point in the future, there's a meteor strike, which wipes all this stuff out. What comes out of the ashes is whatever the DM wants: the Realms, Greyhawk, Krynn, Athas, or even your homebrew world.