I think that we should all pray to God, and ask him not to end the world in 2012. I think that the date is possibly God's planned end of the world since that calender was right on other things. It's also possible that that date is not God's planned end of the world too. We just don't know.
Overall I think God listens to our prayers, and would want us to let him know that we would not like it to end. If it is His will, and what is best for us, then He will make the final decision. But it doesn't hurt to go to Him in prayer. In my opinion.