Nothing's going to happen. Many writers on the subject of the Mayan calendar have often twisted the facts to support their ideas. Even the notion of it is wrong, as the person who popularised the idea of an apocalypse being predicted by the Mayans is actually not a Mayanologist at all; I believe he founded Planet Ark or some other such chariy, and probably used it as a part of his campaign. As for the rogue planet Nibiru coming through, the woman who is making those claims says aliens told her through an implant in her brain.
The idea that the Mayans could predict the end of the world half a millenium before it happened is ridiculous. If anything, they simply didn't make another calendar because they didn't need to. Their current one wasn't going to run out for another five hundred years, so why bother making another one?