Thing is, there is about a page of Greyhawk in Ghosts of Saltmarsh. It's pretty much setting neutral other than that. Sure, it's putatively set in Greyhawk, but, setting it anywhere else isn't a whole lot of work. One certainly doesn't need any knowledge of Greyhawk to run the module.That's a good question. Dark Sun had a release in 4e, so it probably did shoot a bit of adrenaline in the memory of gamers who went over to 5e. What percentage of 5e gamers remembered Greyhawk? And yet there is a Ghosts of Saltmarsh book. Or how about those 5e gamers you mention who remembered Ravenloft? It doesn't require psionics, but the point is that memory for a setting doesn't necessarily mean that the publishers have forgotten it and don't desire publishing for the setting.
And, again, Ravenloft was released VERY early in 5e's run. As in 2016 when the market was about half the size it is now. So, it would have been written in 2015, when, although 5e was certainly gaining steam and doing really well, it was still being marketted directly to nostagia.
Look, I'm not saying you're wrong. I'm just bringing up the counter argument. Dark Sun is a pretty dim memory and likely something the majority of 5e gamers have never even heard of. I do hope that it hits that 70% mark that's getting bandied about. That would be groovy. But, I do think that folks need to understand that it's becoming less and less likely. I mean, that poll that was linked above put Dark Sun at 25%. That's the death knell of the setting. If only a quarter of the people on En World are interested in seeing it, how much less do think the general public would like to see it?
See, but that's the problem again. 40% isn't good enough. That's DM's Guild territory. Which, again, I hope I'm wrong, but, if that 70% mark is the guideline, then, well, none of those settings have enough interest. Ghosts of Saltmarsh largely got a shot in the arm because there were no naval rules in 5e to speak of and no piratey setting. Naval stuff and pirates are always popular. I remember in 3e that I owned at least 5 different d20 D&D rulesets for running sea campaigns. It was very, very popular. So, we get a Ghosts of Saltmarsh.Even with viruses, I don't think the over 50s are dying off that quickly...
And nostalgia and retogaming has never been more popular.
This poll 5E - Which three topics do you most want to receive official (WotC) treatment? from last week has Dark Sun on a whopping 27%, behind only Planescape (on an even more whopping 40%).
But, if a given setting can't even break the 50% mark, well, it's probably not going to happen.