No and no.
Mayans have ever said anything about it being anything.
Without going into too much details and oversimplifying: Long story short, the mayan calandar in question (there are 2 used for different reasons) mostly deals with cycles with the day being the smallest unit. So you count of (20 AFAIR) days, once you reach the end of that cycle, it starts over and increases the count of the next unit, once that count of that unit reaches its maximum it increases the count of the next unit over, etc... etc... Think of it like interlocking cogs of different sizes turning together like a massive clock.
What's happening is that on December 21, 2012 the typical representation of the long count date would reach its roll-over point. Some people are taking that as the Mayans knew that the world was ending... Unfortunately for them, there are even more units higher that are just not typically added to the long count and if I remember correctly there are records of dates going passed Dec 21, 2012 using those units. :P