Bacause:
- I would like some of the mechanics updated to 4e.
- My copies of the original Gazetteer are long gone.
- I never bought the boxed set in the first place.
- I would really like to have a codified collection of Greyhawk lore in one or two easy to read books.
- I would rather buy a shiny new Player's and Campagin guide than buy a beat up copy on eBay.
- I am completely uninterested in the 2e developments.
- I have the disposable income to do so.
Part of the pattern of player's guides has been new races and feats. I can't think of any off the top of my head. Unfortunatly, I percieve this as a strike against the future of the books. That's one of the reasons I think that a pair of books from Greyhawk circa 1983 (?) would have the best chance for selling.
and really Greyhawk got replaced by the Realms in third edition.
2. People are forgetting that FR and Eberron isn't just about 'core' PHB races like Draognborn and Tielflings. Goliaths, Devas, etc... will have to have a place in the reimagined Greyhawk as well.
If they do ever get around to releasing a 4E Greyhawk, I wouldn't be surprised if it is released in the waning days of 4E's market lifetime.
Recall that the 3.5E "Expedition to the Ruins of Greyhawk" book was released the same month that 4E D&D was announced at gencon 2007.