No sir, if they Mayans were so good at predicting... Why are they all dead!?
Well, they're not dead. Their descendants are alive, but maybe they were so good at predicting that they thought "Why do we need a calendar that goes past 2012, we won't be around as a people, then", so they stopped making dates past that on their calendar. Then, outsiders came along and thought, hmmm, an ending calendar. I've got it! The end of the calendar must represent the end of the world!