I don't speak for the OJ definitively but I have a good feel for its staff.
Ideally when I write articles for Greyhawk I try for editionless content. Of course you'll have a need for stats or module info eventually. OJ has been mainly defacto 3.x edition rules for some time now, which is at least backward compatible for fans of older editions. I don't see the OJ putting out any 4e material until there is an outpouring of interest for 4e material or someone steps up to champion it with a slew of useful conversions for Greyhawk. It only takes one person and it could take off, plus who knows, when WotC finally decides to do a full on return to Greyhawk in 4e, that author would be ahead of the game...