Nothing is official, but the internal thought with WWE is that The Undertaker is basically retired, which explains Michelle McCool's departure to stay at home with him. According to The Wrestling Observer Newsletter, physically Undertaker is in far worse shape than is being let on. The company is not ruling out him wrestling next year at Wrestlemania, however, they are not expecting him to work another match before then. His friends have talked to him about winning again at Wrestlemania 28, and retiring with a 20-0 Mania streak.
Damn. So, if somehow Taker gets back into a good enough shape by next March, WM28 will be his absolutely last match.