People think that the world is going to end in 2012 because the Mayan calendar ends at the end of 2012. But the thing is they can't make the calendar go on forever they already made it go for like 100 years! can't go on forever. So honestly its really whatever you believe. My religion says other wise:)
A lot of people think it will because the Mayan Calendar ended on December 21, 2012. But just because the Mayan's couldn't find a bigger rock to put their calendar on doesn't mean the world will end on that day (or even this year, for that matter). No one can predict precisely when the world will end, although people who believe the Bible can look at the prophecies (from Isiah, Daniel, Revelation, ect.) and can tell when it is close.