Joh 21:21-23 KJV Peter seeing him saith to Jesus, Lord, and what shall this man do? (22) Jesus saith unto him, If I will that he tarry till I come, what is that to thee? follow thou me. (23) Then went this saying abroad among the brethren, that that disciple should not die: yet Jesus said not unto him, He shall not die; but, If I will that he tarry till I come, what is that to thee?
A couple of thoughts,
1. We do not particularly need to know what another man's job is or where his path will lead him, it's none of our business.
2. Never assume that what is "in the wind" is true, even among the church.
Moffatt states it a bit clearer;
Joh 21:21-23 Moffatt NT (21) So, on catching sight of him, Peter said to Jesus, "And what about him, Lord?" (22) Jesus replied, "If I choose that he should survive till I come back, what does that matter to you? Follow me yourself." (23) This started the report among the brotherhood that the said disciple was not to die. Jesus, however, did not say he was not to die; what he said was, "If I choose that he should survive till I come back, what does that matter to you?"
I imagine it was a rather innocent question on Peter's part and the Lord eloquently told him to mind his own business, and secondly, check your rumors against the facts.
YMMV