My guess (and only IMHO) is that the reason NG isn't producing 4e adventures is that neither the owners of NG nor their stable of writers like 4e sufficiently to produce material for it. Since the release of 4e, their boards have been pretty slow, with few people talking about 4e games they are playing.
If the Demon Lords of NG and their writers were stoked about 4e, I think nothing would stop them from writing kick @ss adventures for 4e.
Well Clark is both the mouthpiece and co-owner of Necromancer Games, as well as an author of various bits of material for them over the years. He was also the biggest cheerleader on all of ENWorld for 4E and especially for 4E being opened up to 3rd party mor than it was originally set to be. I really don't expect to hear that lack of enthusiasm for the edition is the problem, at least not for Clark.