He needs to go back to the drawing board if he wants to challenge for a title again, otherwise he may fall off the radar. He should work a lot more on his fitness, and maybe look to come in at 235lbs or so. Continuing to try and improve his boxing skills and defensive skills wouldn't hurt also.
I'm not sure whether he was ever good enough in the first place.
He needs to fight someone he can knock out.
I wouldn't be surprised if Peter's career ends here. He might fight a few more times but he will never get back to being a world champion again in my opinion.