If Greyhawk did get a new setting book, in what time period would it be set? I don't particularly like the From The Ashes universe where Evil has conquered much of the map, I prefer Gygax's original version with Evil gathering, hovering on the edge of some big disaster, that yet may be averted.
In fact that's generally true of campaign settings, the original version is usually the prelude to a big war or confrontation, so there's a sense of rising tension, followed by a denoument. This makes for a better story.
When the timeline is moved on, you lose that. So I prefer either sticking with the original, or creating an entirely new setting.