2012 will not end the world. I know when the world will end. And I'll tell you. Before you ask, I'm a Christian, who believes the Bible is the FINAL AUTHORITY. That mean homosexuality, sex before marriage (fornication), and a number of other things are all SINFUL, i.e. WRONG.
Here's what will REALLY happen. The Rapture will occur. This is when Christ, the God-Man, will take all CURRENT Christians to heaven. Does this mean after the Rapture you going to go to hell? Absolutely not! Revelations says that there WILL BE Christians during the Judgement. After the Rapture, you've got seven years. The only way you can't be saved after that is if you take the Mark of the Beast, which means that you follow and serve the Antichrist. People will claim that he is God, but HE IS NOT.
Keep in mind here that I am NOT trying to say, 'Accept Christ or else you're not going to heaven' (though this is true). While I would be OVERJOYED if you became a Christian from reading this post (albeit skeptical at first), I WILL NOT try to FORCE Christ upon you. That would not be right. If you want to know how to become a TRUE Christian, then go out, buy a REAL Bible, not the Joel Osteen 'Your Life Now' Bible. A good recommendation is a Nelson or MacArthur Study Bible. These have GOOD (that is, doctrinally sound) notes in them, to help the reader understand.
Anyways, that is what would REALLY happen. Will Armeggedon occur in 2012? No. If it was going to, I wouldn't be here telling you this. Could it happen seven years from now? It's certainly possible.
And no, people who become Christians after the Rapture will not try to make the world end, just to fulfill the prophecies of the Book of Revelations. If your curious what Revelations is abut, then buy a Bible and read it. That's the only simple way to do it.
EDIT: as for the MOVIE 2012, I think it looks like an excellent FICTIONAL story to go see in a movie theater.