New edition? New setting. It'd need to be a generic setting, yes, but even if it's generic it's still new. 4e with Nentir Vale is thus far the only one that's got this right.
For 5e, the area around Lost Mine of Phandelver should have been a tease region for a whole new setting, released side-along with the three core books.
It bears repeating that both Lost Mines of Phandelver and the Nentir Vale came largely out of the mind of designer Rich Baker, who likely took quite a bit of inspiration for Nentir Vale from the Elsir Vale in his 3.X adventure Red Hand of Doom.
LOL. And people absolutely lost their naughty word over 4e's lore changes. They changed the lore for many of the monsters to fit in the new setting. Changed the cosmology and folks blew their freaking minds. And, with all the screaming over how they are not putting out enough material for the larger Forgotten Realms, only the Sword Coast, could you imagine how much screaming there would be if there were NO Forgotten Realms material? :WOW:
New edition, new setting? Yeah, good luck with that. We saw what happened in 4e.
It's actually not a fundamentally bad idea, at least if there is some continued support for past settings. I kinda like @Lanefan
's idea. On a metatextual level it could represent the growing macrocosm of the shared D&D universe. When a new edition is born, so too is a new setting.
From my point of view, it's usually:
Change I don't like=pointless change, change for change's sake, waste of time.
Change I do like = brilliant designer, kudos, well done.
IOW, official lore is only as important as a measure of how much Person A likes something. It's not important for any actual reason. Just important because "I" happen to like it. And it works as the perfect argument against change.
The Canon Club is largely just a cheap way to try to force preferences on other people.
Hussar's First Law Of Canon
The degree to which canon is important is inversely proportional to the degree to which someone dislikes a change.
I'm admittedly of a mixed mind about canon, which may play into your point quite handsomely.
IMHO, I don't necessarily think that like or dislike of canon or the changing thereof can be reduced simply to a matter of whether someone likes/dislikes change. It seems like too much of a reductionism that marginalizes some of the complexities of people and their attitudes towards canonicity because people do have emotional relations to canon that amounts to more than like/dislike. I certainly acknowledge that if someone likes the change to setting or dislikes the change to setting then that will undoubtedly factor into their receptivity to the changes.
As a point, I'm not really a big believer of notions of "head canon" and the like because, IMO, "head canon" is about like saying that a single fish represents a school of fish. Again IMO, a big part of what makes "canon" canon is that it represents an agreed upon body of texts, facts, principles, etc. of a group or community. And so an important political - because yes it's political - is the idea that what is being included as canon says a lot about who is being included. Canon is often important because it communicates shared assumptions within a community or even between communities. And as silly as it may sound, people have built their identities in relation to various canons of fandom so when disruption occurs to canon, then a disruption can occur within fandoms.