So? What? The transfiguration is not the fulfillment of Matthew 16:28, Luke 9:27, Mark 9:1. You make Christ appear ridiculous with the timeline He gave by forcing it to mean 'some of you will not die within the next week'. It also makes Christ appear ridiculous in His words when, after the transfiguration, He commanded them to tell no man about it when He Himself had spoken of it to many (disciples) a week earlier.
You make Christ appear ridiculous by having Him say, some of you will see the Son of man in AD 70 when nobody saw Him then at all. You make Him out to be a fantasist or a liar. What He says, in effect, to the disciples is, "Most of you are not going to see My coming since it is far into the future, but some of you are going to do just that." And they did, and Peter tells us that He saw His
'coming.' Why won't you believe him?
The significance of the transfiguration lies in the words that came from the cloud, "This is my beloved Son, in whom I am well pleased; hear ye him". "Hear ye Him" over what was represented by Moses and Elijah, i.e., the law and the prophets. It was like the passing of the torch. It's also significant that the three Christ selected were the same three designated as 'apostles to the circumcision' [Galatians 2:9].
The significance of the Transfiguration is that Peter, James and John saw the exalted Christ (Matthew 17:2) and saw, in small measure, the dead raised.. To be sure they also heard the Father's voice, but that had been heard previously at His baptism. Your bit about 'apostles to the circumcision is moot because Paul also saw the risen Christ (1 Cor. 9:1).
When Peter was speaking about being
'eyewitnesses of His majesty' (2 Peter 1:16), he could have talked about the Lord Jesus healing a man born blind, raising Lazarus, walking on the water, raised from the dead, but he doesn't. The Transfiguration was the most amazing thing he had seen because it was
'the power and coming of the Lord Jesus Christ.'
Yea, that's some real answer. As I said, this....:
27 But I tell you of a truth, There are some of them that stand here, who shall in no wise taste of death, till they see the kingdom of God.
See above.
31 Even so ye also, when ye see these things coming to pass, know ye that the kingdom of God is nigh.
What things were those?
'And there will be signs in sun and moon and stars, and upon the earth, distress of nations in perplexity and the roaring of the surging sea. People will be fainting from fear and apprehension of the things that will happen to the world, for the powers of heaven will be shaken. And then they will see the Son of Man coming in a cloud, with power and great glory' (Luke 21:25-27).
Your problem in a nutshell is that none of these things happened in AD 70.
32 Verily I say unto you, This generation shall not pass away, till all things be accomplished. Lu 21
....does not 'fit' your view. That's the problem in a nutshell.
The verse, as it stands in Luke 21, would indicate that
genea here stands for 'race' or 'people' (cf. Deuteronomy 32:5; Psalm 12:7; Psalm 78:6-8), and indeed they haven't. Quite simply,
'all things' were not accomplished in AD 70; nor did Christ return with
'power and great glory' in AD 70. If one compares with the parallel passages in Matthew and Mark, it becomes clear that
genea can indeed refer to 'generation' and to AD 70, but that the coming of Christ comes afterwards (Mark 13:32 etc.).
The kingdom of God was revealed, small as a mustard seed (Mark 4:30-32), with the first coming of the Lord Jesus. He repeatedly refers to it as a present entity (Matthew 5:2, 20; 11:12; 12:28; 18:4).
"And this Gospel of the kingdom will be preached in all the world as a witness to all nations, and then the end will come" (Matthew 24:14). It hasn't been completed yet, but the day is surely drawing close.