Regarding The Undertaker's wrestling status, the mentality of WWE personnel is that he's considered retired. This explains Michelle McCool leaving to spend more time with him at home.
The Undertaker is in far worse physical shape than is being let on. While company officials aren't ruling The Deadman out for a match at Wrestlemania XXVIII, he is not expected to compete before then. People close to the legend have talked to him about retiring at the event.