The Undertaker, Sting, Kane, Big Show, Mark Henry, and Christian. All sometime within the next two or three years, tops.
The Undertaker capping off his twenty-five years in the company by hanging them up after next year's Wrestlemania would be a fitting end to his storied career, and 32 being Taker's "last ride" would a good selling point (one of them, anyway) for the huge event they want next year's Mania to be. Mark Henry has already talked about retiring next year. Sting may never wrestle again as it is. Christian already feels unofficially retired, since he hasn't wrestled a match in nearly two years and the the 2014 Elimination Chamber was the last time I can remember seeing him step in the ring. Kane and Big Show speak for themselves.
