Personally, I would love to see a new Greyhawk released. My own personal opinion is that there are only three requirements:
1. The Darlene Map. I mean .... c'mon.
2. Try to keep the sense of mystery. I may have a preference, but I don't care what timeline they eventually settle on. But what I would like is that the follow the Folio/Campaign Setting example and have it full of mystery and hooks that DMs can choose to expand on in their home campaigns.
3. Make it interesting. Nothing about the old setting is sacred. I just want something good that is appealing to new players as well. There are so many different "takes" they could use- a GoT-style politics setting, or a S&S + gonzo setting, or a "barely holding on to civilization" setting, or some other take. Just take a point of view and stick with it.
I could certainly live with this. I think that one of the bigger draws, at least for me, of Greyhawk is the fact that it wasn't all colored in. There are lots of "Here be Dragons" type areas to use as my own personal playground. I find that Forgotten Realms is fantastic to run as a Forgotten Realms campaign - where I can draw on all that material and weave it together into a campaign. I find that Greyhawk is better for a Hussarhawk campaign where I can sort of pick and choose bits and bobs that I want to use, but, because there is so much white space on the canvas, I can do a lot more of my own thing.
Granted, you can certainly do that in Forgotten Realms, but, for me, that's missing the point of the Realms. Why use FR if I'm not going to take advantage of all that material?
Dunno if that makes sense, but, that's how I feel about it.
Although, one quibble, @Snarf Zagyg. While I ADORE the Darlene maps, the Anna Meyer maps are just jaw droppingly gorgeous and I would be very happy to see them used instead of Darlene.
OTOH, that's basically having two jaw droppingly gorgeous options, so, neither one is a loss.