After speaking with sources, WZ has learned that WWE involved Shawn Michaels in the Hell in a Cell match between Triple H and The Undertaker with a tentative plan to set up HBK's involvement at WrestleMania 29.
It is believed that the current plan in mind is to run some kind of finish to the Hell in a Cell match that causes Triple H to call out Shawn Michaels the next night on RAW.
The plan that is circulating behind the scenes in WWE is that Triple H and HBK would have a verbal confrontation that leads to a match at WrestleMania 29.
It has been reported that WWE wants to announce one of the big matches for WrestleMania 29 soon, giving a year to promote it just as they did with The Rock and John Cena – an HBK vs HHH match could be that main event bout.
Source: http://wrestlezone.com/news/251981-exclusive-details-on-wrestlemania-29-main-event-being-considered