Problem is the Mayans never predicted the end of the world. It's crazy people that like to sensationalize things that made that up. Any one who actually studied the Mayans would know that it's just the end of an era.
The Mayans had eras called Bak Tun's, see the Maya saw time as circular, not linear like we do today. There was no past, present or future, time and everything in it repeated itself.
So when the Mayan calendar ended on Dec 21st 2012, it was just the end of a Bak Tun, nothing more. If the Mayan civilization didn't end, then they would have continued the calendar to another era.