Contradiction with Matthew 24:36
This verse states that no one knows the day or hour of the end, not even Jesus or the angels, whereas John 21:22 suggests Jesus knows the future of John's life.
Matthew 24:36: But of that day and hour knoweth no [man], no, not the angels of heaven, but my Father only.
Contradiction with Acts 1:7
Jesus says it is not for the disciples to know the times or seasons which the Father has put in His own power, contradicting the implication in John 21:22 that Jesus has a say in John's future.
Acts 1:7: And he said unto them, It is not for you to know the times or the seasons, which the Father hath put in his own power.