Wikipedia reckons October 2008 (here). I seem to remember reading something saying they might skip it altogether, but I can't remember where. Doesn't look like it will be any time soon though.
i think one of the things holding back 802.11n is other technologies such as hsdpa and wimax.
Whislt they dont offer the speed that 802.11n has, they do offer wireless companies like mobile operators the bility to create man's across urban sprawls. Essentially, its easier to make money with technology like wimax meaning that others like 802.11n may never see the light of day in an official form as beady points out.