As a guideline, like everything in this game: no. In my 25+ years of DMing, I have fudged very occasionally, but usually to make it harder for the PCs (I have never ended a fight early), but I had an evil druid NPC that wild shaped onto a hawk and flew away (to maybe come back later), only for...
Perfect, absolutely dig, they just keep nailing it for me with this edition. There is no need at this point to release a fifth FR campaign setting book/boxed set, etc.
Most of Planescape (my favourite setting) is fluff, so, no need, regardless! I have converted most of the major Planescape races and monsters (Bauriar, Dvati, Guardinals, Rilmani, etc) to 5th Ed, so I am good to go.
Ah, I can dig, my time is precious too, but I enjoy designing and converting as much as DMing/playing, just in a different way.
Converted the Favoured Soul at work today (took less than an hour).
The Shaar is Northern Africa (wemics, etc), the Native Americans are across the sea in Poscadar, in northern Maztica.
There is also the continent of Katashaka, the Land of the Tarrasque (Africa), below Maztica, and you have Osse (the continent south-east of Zakahara), which is basically...
I do not think 5th Ed's "success" is reliant on releasing campaign settings. Also, WotC has released a ton of previous edition material as PDFs (which new, younger players might actually prefer - "Mommy, what is a paperback?").
I love all of those settings, but thinking about it, the material already out there is eminently useable with 5th Ed, no real need for yet another FR campaign setting book/boxed set, we have 4 now.
Depends how you approach it, like, GH, FR, DL, etc, exist in all Spelljammer campaigns, but Spelljammer does not exist in all GH, FR, DL, etc, campaigns.