It won't happen because the 2012 the Mayans predicted already occurred due to daylight savings, which didn't exist then.
It would have nothing to do with daylight savings. A full year has the same number of hours regardless of whether or not we use daylight savings. All it does is adjust the time forward one hour, then back one hour, to a net change of 0 hours.
Maybe you mean leap years? I believe that theory was debunked, seeing as Mayans used a more accurate calendar than we do and they had no need for leap years.