I think WWE are going to keep this ' returning superstars' ID a secret untill he actually walks down that ramp on 2nd January's edition of Raw. If it was anyone else ( other than Undertaker) like Chris Jericho, Shane & Stephanie or even another wrestler from the past, they would have possibly revealed his or her ID a lot sooner. Because of Undertaker's mysterious nature, they are not going to be in a hurry to reveal when he is going to actually return to the WWE. Even though I might be wrong as well, but I would take more notice of WWE than most websites regarding possible returning superstar rumours.
There's no escape from THE DEADMAN!!!