According to the latest issue of the Wresting Observer Newsletter CM Punk's three year contract with the WWE is set to expire in the Summer of 2014 and Punk himself has said on several occasions that he's not going to stay in pro wrestling as long as some fans think.
Punk has been dealing with various injuries over the past few years and he's not nearly as loyal to painkillers as most pro wrestlers are, due to his straight edge lifestyle.
If Punk does indeed leave the WWE after his contract expires I think that he's a guy who would do very well outside of pro wrestling.
He enjoys MMA, Video Games and other forms of entertainment so if he chose to, he could pursue other outlets after his retirement and he certainly wouldn't be put out to pasture like some pro wrestlers who retire.
It's speculated that some possible surprise WWE Royal Rumble 2014 Entrants could be Sheamus & Christian. Another possible entry in the Rumble Match could be Chris Jericho, considering that both Sheamus & Jericho will be at the same auto show in Pittsburgh the same weekend as the Royal Rumble.