Seems like a pure nostalgia play, as most players can't tell the difference between the various high fantasy medieval settings anyway.
I agree, they could easily just do an all new clean-sheet setting like they did with 4e.
But I can see Wotc's reasoning though:
"Greyhawk" works for them because it has been a while since they have done anything for it; So new players will not have a real clue.
Those that do know will go for the nostalgia berries "because GreyHawk!"
So Wotc will can write neu-Greyhawk into whatever they want it to be, just like every setting reboot they have done for 5e. While playing on people's nostalgia at the same time.
It's almost like people have trouble accepting that their preferences are mostly set in their formative years, those preferences are difficult to change once they're set, ...
Yes people have preferences, but some things are just classics that stand the test of time.
Works like Shakespeare's, and Tolkien's writings; both of which I can walk into any US books store and find copies of, will be around long after D&D 7th edition is making way for D&D 8th edition...
A lot of the dissatisfaction here has to do with the fact that may of the older "official" D&D settings have been repeatedly altered to fit what the game designers have done with new editions.
To a large degree, I think many fans are just tired with the continual retconning.
For this very reason:
Again, with the brand build up, it is expected that at least some people around the table are familiar with a setting. Which goes back to my original point that a known setting is a shorthand between the DM and players, and making major changes misaligns those understandings and at that point it's better to just homebrew.
As for this:
... that those preferences won't continue to be catered to as they get older and less relevant in the marketplace.
It's clearly a crapshoot when you update things for:
"Modern Audiences."
The DragonLance setting/Adventure/Wargame reboot didn't really do all that hot. Were there some things in the original setting that could do with a change? Sure. But you can also go too far and fail to stick the landing, which is what happened.
And new products specifically created from the ground up by and for the "modern audience", like
'Journey's Through The Radiant Citadel' have been among the lowest sellers in 5e's product portfolio.
There are very good reasons why Wotc keeps going back to the nostalgia well, rather than creating all new content. Even then it is a balancing act that they clearly have a hard time getting right.
In my opinion; Given Wotc's track record when they try their hand at 'updating' older settings, it should not be controversial that many fans will be skeptical of the dev's ability to execute.