Though it may lead some people to atheism, I don't think it will be any spectacular change. In fact, I won't be surprised at all if many people find some way to blame science and scientists for their fear of 2012 in the first place (History Channel, I'm lookin' at you).
When people are firmly convinced that the world will end on a specific date, and then it doesn't - they decide that something saved the world. In one case the members of this cult were congratulating each other for hte "fact" that their faith and purity saved the world! This came up during the section on Cognitive Dissonance in Psychology classes way back in University.
Besides, it will be easy for non-Mayans to dismiss the 2012 Mayan calendar thing that they are taking so seriously now, and Mayans don't believe that nothingness follows the end of the world but rather that it is created anew, as it has been several times in the past, so they won't have any issues with surviving it.