Well, obviously...the Mayans were wrong (shock and surprise...right?) So, now that everyone who bought 400 gallons of bottled water and moved to a tunnel bunker in the desert looks foolish, we can move on with the real world.
The way I see it, some guy with a rock and a chisel hammering out that calender about 2,000 years ago said, "Forget it!!! I have made this calender up to the year 2012 and the galactic alignment!!! I won't be here to see that far in the future...someone else can finish this stupid thing!!!" Then they decided that was good enough for them.