In one his latest blogs, JR says he agrees with WWE to keep The Undertaker off TV until WM31 and will be ready:
I completely agree with WWE as it relates to Undertaker not being seen in person until his entrance at WrestleMania. I know the ‘Big Dog’ has been training like a MMA fighter preparing for a title bout so he will be ready without question.
I couldn’t agree more. The Undertaker WILL be ready. If there was an ounce of doubt about that, even for a split second, Taker would not even consider coming back. A professional like Taker won’t work the biggest show of the company he works for with doubt(s.)