the ones that come my mind, when thinking about retirement, are the undertaker, kane, edge, rey mysterio, and HHH the reasons:
Undertaker: obviously age and injuries have taken their toll on the dead man, and it was already stated that he wanted his last run to be with paul bearer, so..., and undetaker is also has a real estate business
Kane

glenn jacobs) been around for awhile too(isaac yankem, fake diesel), so age and injuries have plagued him too, he is very involved in politics, and if is him, could explain the sudden push for champion, if he goin out let him go out on top
edge:although still young compared to the others, he has sum serious injuries, he already stated the he thinking bout retirement, and he financially well off where he wouldn't need to wrestle anymore
Rey mysterio: like kane and taker, age and injuries gotta be catching up to the high flyer, don't know what he'd do out of the ring, maybe instructor or something
HHH: same as the others age and injuries, and with him gettin the adviser job, he'd still be around just not wrestling
those the ones that i think of when it comes to retirement, which ever it is, a big hole will be left in their place, all are superstars, all are future hall of fame.