Of course 2012 is going to be the end of it all.
Except it's not really an asteroid.
It's a man made construct, based on alien technology and was built by the US government in secret at Aera 51 during the mid 1950's.
It's original purpose was to wipe out those pesky commie *******s in Russia.
They used a conjunction of time travel and warp technology to set the objects starting point and then pressed the 'go' button.
God himself was consulted and he gave the project the green light (better dead than red, right ?) - In fact, he even let Jesus paint the racing stripes on it.
President Eisenhower wasn't told any of this to maintain plausible denial and accountability in the following aftermath and demise of the CCCP. A tradition and a 'loosely kept' secret upheld to this day.
How the Mayans actually 'predicted' all of this was because a few Area 51 scientists got very drunk one night and took the time machine for a quick spin and visited the Mayans. (One of the scientists was fascinated with them).
Using alien translator tech, the scientists told the Mayans of their plan. However, since the scientists were pretty drunk and the alien language translator wasn't calibrated for 'drunk speak', the Mayans only got half of the story. They got 'asteroid' and '2012' - but that was about it.
Why 2012 was chosen, is the real mystery. No living soul knows why that particular year was chosen.
The General in charge of the project along with several key staff members were killed in a plane crash over the Nevada desert in 1958.
Meanwhile, the scientists recalculated their math and discovered that instead of only wiping out Russia, their object was going to destroy the entire planet. Anecdotal evidence suggests that the scientists panicked and once more took the time machine, presumably to go back in time to correct their calculations but have not been heard from ever again.
Their whereabouts / whenabouts are unknown, along with the time machine itself.
The few remaining project members who were not in the decision making loop were quietly 'taken care of' by the government in an effort to keep this 'secret' hidden.
Only God knows the answers but he's keeping pretty tight lipped about it all and is refusing to take any calls.