When I first heard that Roland Emmerich would direct another disaster themed movie, my first thought was, is he going to make a sequel to, The Day After Tomorrow, Godzilla or Independence Day. This was not the case.
This time Emmerich found his disaster in the doomsday predictions surrounding the year 2012.
The reason that some people believe that the world will seize to exists, as we know it in December 2012, is that the Mayan calendar stops there. However, there has been numerous of similar predictions over the years, and we are still here, so I would not feel that anxious about it, if I were you.
I guess that the Mayas stopped creating their calendar; just because they thought that, it was simply enough.