As said above, a very interesting topic even though I'm among those heretics leaning toward the conclusion that the "special" thing with the 2012
date is simply the "re-start" of a cycle, rather than any necessarily cataclysmic event.
Compare the Mexican calendar, which is basically identical to the Mayan apart from the long count. They also counted on time running in cycles rather
than in the linear fashion of the modern world. That includes the belief that if one thing happened on a certain date in the past, it must necessarily
happen again on the next occurrence of that date. Conversely, if something important happened today, it must obviously have happened already at the
previous point in the circle, and so on.
Check out Susan D. Gillespie's "The Aztec Kings (the Construction of Rulership in Mexica History)" for how the so-called Aztecs may have handled
problems with a) things supposed to happen at certain times and b) completely unexpected things without precedence in the calendar/chronicles. (Hint
for b: re-write the past...)
Anyway, seeing as how there are loads of different Mexican chronicles giving different years for events, varying numbers of previous "Worlds" (3?
4?) and such, how widespread is this particular Mayan time frame? Pan-Mayan, found among the Mayan peoples of one or two regions (Guatemala?), or just
a Popol Vuh thing? Here's a quote from an old photocopied article from some religious encyclopedia (I have no idea which, I'm afraid, but it's
pretty modern - as from no earlier than the Eighties or so):
"But the Maya, like some of their predecessors who were exposed to Olmec influence, could also compute any date in terms of the Long Count, in which
a fixed date, corresponding to a day in the year 3133 BCE (probably representing the beginning of the present cosmic age), was taken as the point of
departure. The end of the Long Count's cycle will occur on a date equivalent to 24 December 2011." (No, that's not a misprint; that's what the
page says. It continues and a bit later refers to that faraway date someone already mentioned

"The wisdom of the calendar was indeed the key to
penetrating the mysterious rhythms of what exists and becomes. This probably explains why the priests were also interested in the computation of dates
in the distant past. On Stela F of Quirigua is inscribed a date, 1 Ahau, 18 Yaxkin, that corresponds to a day 91,683,930 years in the past!"