When will the Undertaker return?

The Undertaker has a torn rotator cuff last fall and he went into Wrestlemania XXVII still recovering from that and the match that he had with Triple H at Wrestlemania XXVII was very physical. This was one of the very few times that I can remember The Undertaker being carried out on a stretcher. Mark Calawat aka The Undertaker is also taking care of his wife Michelle McCool who retired from the WWE this year and has several injuries that she is recovering from. I don't think The Undertaker has a definite timetable for his return. We may not see him until the Royal Rumble and the shows leading up to Wrestlemania XXVIII.