Scribe
Legend
Well, Wildemont got an AP (Netherdeep) and Darrington Press released a large amount of 3pp support. If any setting had a chance, it was that one. But you kinda supported my point; so far only Faerun, Eberron and Ravenloft got any sort of ongoing support. SJ, PS, DL, and GH all have token support so far (and we don't know what format DS will take).
I don't consider 3PP settings here.
It needs to be Wizards, with a real push, multiple adventures, source books, and marketing.
Otherwise, no way it will spread to the wider more disconnected (offline) player base.