The Mayans did not think that the world will end at the end of the cycle of their calendar. They even had dates beyond 2012.
Since it is a cycle and there are only four elements in nature, fire, earth, water, and air, the cycle will repeat with the first one--fire. And this may mean that the destruction will be by fire. A nuclear World War III as I explain below may be that fire. And the earth will be enveloped by smoke for a year. There will be no place in this world where we can hide without being affected by the coming war.