Mark 8:31-9:1 (which also has parallels in both Matthew and Luke) states that some of those standing before him would not die until the Kingdom of God had come. They are now dead, and the Kingdom is not here. So again, it shows he failed.
Matthew 16v28 B ...not taste death until they see the Son of man coming in his kingdom or royal government.
How did they see Jesus? ______ According to Matthew 17v9 it was in a 'vision'.
They saw a future 'vision' of Jesus coming in 'glory' see Matthew 25v31,32.
So before they died they saw in the 'vision' that Jesus said to tell the 'vision' to man man until after he was resurrected.
It was not a literal happening, but as Jesus said it was a 'vision'.