I suspect the
GSL will pretty much be an "adventures and only adventures" type deal for
4e.
WOTC wants the small publishers to do the stuff they think they can't sell. This isn't new, its what they wanted last time but the
OGL kinda crimped that.
Also it wouldn't surprise me if
WOTC's adventures will be "gotta get em all" kinda deals with extra content stuck in them as a sales spur -- Want to use the XYZ feat/paragon path than you need Temple of Damnation Adventure.
By next addition
WOTC will be all closed content ...