It looks like we now have 3 types of setting books.
1. Full Setting - Primarily about the world and it's mechanics, with a short introductory adventure. Ravnica, Ebberon. Looks like we will get 1 per year of these.
2. Half Setting - Mix of mechanics around a theme with half the book dedicated to adventures around that theme. Ghosts of Saltmarsh.
3. 1/3 Setting - An adventure that also does duty as a setting guide, but doesn't introduce much in the way of new mechanics. Curse of Strahd, Storm Kings Thunder, Out of the Abyss, Tomb of Annihilation, Waterdeep: Dragon Heist
Here is how I'd imagine they will break down
Full Setting - Dark Sun, Fall 2020/21, Something Brand New, Fall 2020/21
Half Setting - Planescape, Spring 2020/21, Feywild/Shadowfell, Spring 2020/21
1/3 Setting - Spelljammer, Summer 2020/21, Dragonlance, Summer 2020/21
Good thoughts, but I'd say you make too much of a distinction between 2 & 3, or perhaps the line is not drawn quite right.
I'd say we can safely catagorize all 5E products so far into 4 boxes:
1.) Generic supplements, useful in most games expanding on the generic D&D world metasetting: Volo's, Mordenkainen's, and Xanathar's Guide books.
2.) Storyline book, so far set in just the FR with new big adventure material and a regional Gazeeter component: Tyranny of Dragons, Elemental Evil, Out of the Abyss, Storm King's Thunder, Tombnof Annhilation, Waterdeep, and Baldur's Gate.
3.) Reprints and expansions of Classic Modules, that include the full text of the old Adventures with additional Gazeeter information and expanded information: Curse of Strahd (which reprints the entire text of Castle Ravenloft), Tales from the Yawning Portal, and Ghosts of Saltmarsh. Arguably, Dungeon of the Mad Mage...
4.) Genre supplements, which provide PHB, DMG, and MM components to really push a certain kind of story using a given world as an example to use or pilfer: Sword Coast Adventurer's Guide, Guildmasters Guide to Ravnica, Rising from the Last War
It seems that Dragonlance is uniquely suited to fill both 3 & 4 in the scheme, with the classic modules and an Epic Fantasy genre book. Most of the other settings don't have quite the same cache in famous, well-remembered modules that Dragonlance and Greyhawk do. Mearls made the case for Greyhawk in a recent interview as a great "generic" place to put non-storyline Adventures.