There's a possibility that Hulk Hogan and Sting could both wrestle their last matches at WrestleMania 31. Hogan has still been pushing for a match against John Cena next year and if he could pass a physical, Hogan may wrestle his retirement match. Cena's WrestleMania 31 match may be locked in already but they could always come up with something else for Hogan.
Sting has indicated that he is looking to do one more match as well. Hogan and Sting both wrestling their last matches could be a big sell for WrestleMania tickets and buys. Hogan will be almost 61 at that time and Sting turns 56 the week of the show. It's a long shot but possible, although both likely wouldn't be branded as retirement matches.