The link in TDG on McKenna and whether or not he really believed in a 2012 apocalypse is like a lot of speculations on this subject - the author is interested in pinning down some specific event or definition when in fact McKenna was probably just "trying on for size" an idea. Sometimes the best thing you can do with an idea is to float it out in humanspace and see what people do with it. McKenna was probably more interested in the reactions to the idea than whether or not it was pointedly true.
McKenna actually believed the "apocalypse" was already upon us via the socialization of hallucinogens in planetary culture, so he was probably kind of curt sometimes because the big change was already taking place right before our very eyes and why don't you see it?
I personally think the planetary aura is shifting a hell of a lot lately due in no small part to the widespread worldwide gifting of orgonite which is Everyman's philosopher's stone, and there are other influences coming to bear and coming to head right now too such as an increasing influx of cosmic rays and the information sharing revolution of the internet which has enormously focused and energized human will, visualization, and intention. To a lot of us out there (pun intended) the apocalypse is already here and you can see it in the eyes of people everywhere. December 21 is already close by, and in fact the date has been passed in every sense.