It should be no surprise that, having played AD&D 1st Edition back int the day, the other kids and I also got into Greyhawk. So I got out my 1st edition booklets and maps again to look that over with mature eyes recently also.
This, folks, is a setting made to be liminal. You have plenty of summary information about climate, weather, nations and their cultures, countries and their politics, big organizations and their major concerns, and major figures (with class, level, and Alignment). You got some tables to spice up your campaigns therein, and some notes to guide your use of the setting, and that's it. You didn't get a plug-and-play product here; you got a parts kit and were expected to build it into a complete rifle on your own.
This is before any Greyhawk novels. This is before the post-Gray Box Forgotten Realms, before Dragonlance, before Eberron, and all of the other settings (and revisions thereof) that increasingly spelled out what was there, who was there, and otherwise increased the density of information such that a canon arose and with it all that a canon calls forth: orthodoxy, and the slavish devotion to it that I sometimes call "Fandumb".
That's fine for a writing bible, the sort used for franchise properties or television shows where having a single reference with authority given to it matters, but for a setting published for use with a tabletop RPG that means unforced errors of one sort or another.
Liminality, in practical terms, means that you provide just enough material for your users to get going at building out their own interpretations for use at their tables. (Yes, this directly undermines the proto-MMORPG that is Organized Play campaigns, and that's a good thing.) Writers can think of this in terms of a prompt. Gamers can think in terms of a scenario premise.
For a tabletop RPG setting, the boxed set for Greyhawk nailed it. So did the original boxed set for the Realms. After that, you ended up having to either learn how to avoid where it's too built up, or demolishing what's present to make room for what you want (and making more work for yourself). Liminality, therefore, is that frontier space where there's enough to go do your thing, but not so much that busybodies start nagging you about it; it's about implication, not canonization. Pulp, not Pink Slime.
Because of this fact, I don't see a future for commercial settings anymore. Wikis do the same thing cheaper and easier with far superior convenience. What I see instead is a future for tools and tutorials to guide users in taking that just enough material and making their own fun from that.