Q. Re: Eyewitnesses To The 2nd Coming. I was taught that all of the Disciples had died, except John who lived to be in his 90’s. On the Isle of Patmos he was given by Jesus Himself, the full Revelation of His Kingdom ! “some of you will not taste death until ….” The disciples didn’t understand what He was saying but He knew that He would appear personally to John and give in detail, that which would occur in the end times.
A. Matt. 16:28, Mark 9:1, and Luke 9:27 all agree on the wording of the Lord’s statement. And these verses are universally translated into English as a plural sentence. “There are some … until they …” If this referred to a time when all the disciples except John had been put to death, the sentence would have been singular. “There is one … until he …”
The only event that meets the plural requirement is the transfiguration. Remember, the Gospels were written under the guidance of the Holy Spirit. In John 14:26 Jesus said the Holy Spirit would remind them of everything He had told them. There could not have been a lack of understanding.