Partial Source: Pwinsider
According to reports, The Undertaker is in much better health these days following WrestleMania 29. He recently appeared in two matches involving The Shield. Reportedly, WWE is keeping the door open for him to return whenever he wants. It is likely he will be involved with The Shield when he returns. After his match with Dean Ambrose last week on SmackDown, 'Taker is likely to stay off television for the time being. He's currently not scheduled to appear at WWE Extreme Rules and was only considered for a match in emergency situations. This would have been if top superstars, such as John Cena, would have been out.
The Undertaker also reportedly changed his diet and workout regime prior to WrestleMania 29. He's also been booked in matches to try and help his body, including what are being called "smart matches" against CM Punk and Ambrose.