Various news sources are reporting that Shawn Michaels plans to retire at Wrestlemania. Apparently, Shawn has been telling friends of his impending retirement at Wrestlemania.
Michaels has talked an awful lot over the past few years about retiring. He has made such a fuss that WWE even started incorporating jokes about it in their storylines.
He also said in a radio interview last year that he had given the company his retirement date, which at that time was this years Wrestlemania. He has considered wrestling into his fifties, but if he does it will probably be just 1-2 matches per year.
Michaels is not advertised for any shows past Wrestlemania, and it is worth noting that The Undertaker is scheduled to appear at shows after the event.
This would explain why Michaels has put his career on the line at Wrestlemania.