"So what is to be done with Greyhawk? I think there are two simple, easy-to-understand, wrong solutions to the problem:
1. Ignore the haters and publish whatever you want; they are just going to whine and die off anyway.
2. Don't bother with Greyhawk; it's not worth it.
The reason neither of these is really suitable is because ignoring the people that are truly passionate about a product is probably not a good way to succeed (after all, even old people can evangelize) while ignoring the ur-setting of D&D in 5e (motto- "We will bring all ur nostalgia to u while also cultivating the twitch peoples") seems like a poor choice."
Greyhawk is WoTC's (via TSR) oldest campaign setting. It would be, for lack of a better word, criminal for them to let it fall into official disuse.
Catering to the Old Guard exclusively is a mug's game. But given that we are almost on the 50th Anniversary of D&D, it would be beyond comprehension for WoTC to not issue a new Greyhawk for a new generation.
Life is all about reboots; for WoTC to forsake one of their classic IPs, and their ur-setting, seems like a poor choice.
I don't know if I agree about not ignoring those who are passionate about a product when it comes to this kind of stuff. Sometimes, I think you have to do that, at least a bit.
I don't know if a Greyhawk product could be made that would meet the criteria that it appears necessary to meet. The requirements of the fans of the classic material may not align with the expectations of modern players and enthusiasts. Yes, there are some people who probably fit into some kind of venn diagram where they enjoy elements of classic play and elements of modern play (I probably fit right into that overlap myself), but would that be enough to justify a product?
For every old school fan of GH who might want a 5E version, you have another who points out he doesn't need it, he's been homebrewing everything he needs for several editions now, anyway....for every person who enjoys things like drow PCs and tieflings, you have a grognard whose head explodes at the meer mention of them.....and so on.
You're obviously very passionate about the setting, and that's cool....like I said, I dig it myself, although I don't think to the same degree. But how much of that is based on nostalgia and other factors that can't be replicated for a new audience?
Yes, you're right that a great product can appeal to a wide audience. So I think the question then is "how do you make a great Greyhawk setting book?" This has been touched upon in this thread, but even in the relatively small sampling here, an idea is posed, and immediately there are those who disagree.
I don't know if it can be done. Or that it can be done again....that may be a better way of saying it.
Maybe taking one of the old versions (either the Folio or the boxed set....but probably more likely the boxed set) and updating it with some modern layout and writing, maybe some sidebars that help reconcile differences between classic gaming and modern gaming (i.e. options being limited vs. many options being included, and so on). Maybe that might work?
Personally, I have no need of such a product, and neither do most existing fans of the setting. They'll only get so much out of it. You seem to want to capture a new generation of fans for the setting. This is not in any way a bad idea.....but I think that the question then becomes: "how do you make Greyhawk seem as awesome to people today as it did to the early gamers?"
And that's kind of tough.