WotC wouldn't sell GH, heck, I doubt they'd even license it except under very specific means of use.
I mean heck, you really think WotC would go through and rename all the Tensers, Bigby's and Wee-Jas' entries just to make a cut of Paizo's products?
That aside, I doubt the products would sell enough to make them profitable. Not because "greyhawk sucks" since I like Greyhawk well enough, but because of the scale of operations. I could of course be wrong, given that Dragonlance is still going, but I think Greyhawk would entail quite a bit more work from WotC in any licensing scheme.