Usain Bolt is about to retire after the 2016 Olympics anyways
http://www.washingtonpost.com/blogs...ays-hell-retire-after-2016-olympics-in-rio-2/
“I spoke to Michael Johnson, who said he retired because there was nothing else left to accomplish,” Bolt, 27, told the Telegraph. “I’m happy to have achieved everything that I have, but when you don’t have anything left then you might as well retire. I would leave the sport to all the young kids coming through, because I hate losing.”