The Mayan calendar does not actually predict anything. It is just an end of a cycle like we have ends of calendar years. OK, it is a long count. However, nothing craved in the stone says what might happen.
I believe they would have just started a new freaking cycle when that one ends.
The date was also miscalculated, http://www.nasa.gov/topics/earth/features/2012-guest.html It is really dec 24th.
BTW, the great alignment they keep talking about that they believe links to the Mayan Calendar, oops it actually already happened,
http://www.nasa.gov/topics/earth/features/2012-alignment.html
Also that being said, the power of the masses is something else. I believe there will be a run on basic supplies by some, others will do nothing.