Today we received word that Sting is back home and is training to cut down on some weight and get in better shape. The feeling among those around him is that while he's not admitting anything that he is training for WWE and wants to look good for his WWE debut. His wrestling debut (and possibly only WWE match) would be at Wrestlemania.
As of right now there are no obvious match-ups available for Sting. Brock Lesnar vs. Undertaker is penciled in for Wrestlemania but I can see them switching that up in favor of an Undertaker/Sting match.