Firstly, I've read several critiques of the prophesies of St. Malachy that cast serious doubts about whether these prophesies are authentic. Apparently, the evidence is that the prophesies appeared long after his death and may have been penned by someone who was trying to influence papal elections around the time they became known. So I have never put much stock into these prophesies.
Secondly, I doubt very much that Bergoglio will step down any time soon. I believe he believes he has a mission and that is to destroy any vestiges of the traditional Church. He hates tradition, he hates Catholic doctrine, he hates unchangeable and irreformable dogma...in short, he hates that Catholic Church. He's not going to leave us on his own accord anytime soon.
Besides, I think he intends to "reconcile" his church to the Lutherans before 2017. And when he does, Voris, et. al., will praise him for bringing the Lutherans back into the Church while he will have actually formally declared the Church to be just another Protestant sect. Maybe Bishop Fellay will finally see the light.