Merlin was not real. He was made by someone named Geoffrey of Monmouth.
I looked up this William Kacy fellow and he was nowhere to be found on the interwebs.
The mayans believe this is the ending of the current cycle we are in. This does not mean that the world will explode when the cycle ends. It just means that the cycle will restart into a new era. This is the same as 1999 - 2000.
I have researched a good amount into the mayan culture and listened a lot to Ian lungold. He's probably the most experience in this subject and he did not say the world was going to blow.