I noticed this thread just now and I haven't looked at the all posts (so someone may have already said what I'm about to share) but I believe I can provide an explanation for some of this confusion, so here goes (I apologize if someone has already posted this). Listing each one of those verses again:
Matthew 16:27(KJV) For the Son of man shall come in the glory of his Father with his angels; and then he shall reward every man according to his works.
Matthew 16:28(KJV) Verily I say unto you, There be some standing here, which shall not taste of death, till they see the Son of man coming in his kingdom.
Matthew16: 27. For the Son of man shall come in the glory of his Father with his angels; and then he shall reward every man according to his works. 28: Truly I say to you, There are some standing here, which shall not taste of death, till they see the Son of man coming in his kingdom.
I believe (in all 3 cases), Jesus is speaking of two different events, 1 in verse 27 and the other in verse 28. In 27, He is speaking of a future event which hasn't occurred yet, which we read about later in the New Testament (end times). The 2nd event occurs shortly thereafter, in the next chapter of Matthew, starting in verse 1 (which is where Chapter 16 left off) which is when Jesus takes 3 of His disciples onto the Mount of Transfiguration where Jesus is transformed into His glorious self, and Moses and Elijah "magically" appear with Him. It was Peter, John and James who I believe that Jesus was referring to when He made the statement that some would see the Kingdom (verse 28) and what Jesus would like when He returns to this earth in His glory. We see this repeat itself in all 3 gospels.
Matthew 17:1-8(KJV) And after six days Jesus taketh Peter, James, and John his brother, and bringeth them up into an high mountain apart,
2 And was transfigured before them: and his face did shine as the sun, and his raiment was white as the light.
3 And, behold, there appeared unto them Moses and Elias talking with him.
4 Then answered Peter, and said unto Jesus, Lord, it is good for us to be here: if thou wilt, let us make here three tabernacles; one for thee, and one for Moses, and one for Elias.
5 While he yet spake, behold, a bright cloud overshadowed them: and behold a voice out of the cloud, which said, This is my beloved Son, in whom I am well pleased; hear ye him.
6 And when the disciples heard it, they fell on their face, and were sore afraid.
7 And Jesus came and touched them, and said, Arise, and be not afraid.
8 And when they had lifted up their eyes, they saw no man, save Jesus only.
Mark 8:38(KJV) Whosoever therefore shall be ashamed of me and of my words in this adulterous and sinful generation; of him also shall the Son of man be ashamed, when he cometh in the glory of his Father with the holy angels.
Note that again He's speaking of the day that He comes to the Earth with His angels to put down all unrighteousness and establish His kingdom here on earth and Mark 9:1 is the continuation hich comes at the end of chapter 8.
Mark 9:1-13(KJV) And he said unto them, Verily I say unto you, That there be some of them that stand here, which shall not taste of death, till they have seen the kingdom of God come with power.
Next is the Mount of Transfiguration:
2 And after six days Jesus taketh with him Peter, and James, and John, and leadeth them up into an high mountain apart by themselves: and he was transfigured before them.
3 And his raiment became shining, exceeding white as snow; so as no fuller on earth can white them.
4 And there appeared unto them Elias with Moses: and they were talking with Jesus.
5 And Peter answered and said to Jesus, Master, it is good for us to be here: and let us make three tabernacles; one for thee, and one for Moses, and one for Elias.
6 For he wist not what to say; for they were sore afraid.
7 And there was a cloud that overshadowed them: and a voice came out of the cloud, saying, This is my beloved Son: hear him.
8 And suddenly, when they had looked round about, they saw no man any more, save Jesus only with themselves.
9 And as they came down from the mountain, he charged them that they should tell no man what things they had seen, till the Son of man were risen from the dead.
10 And they kept that saying with themselves, questioning one with another what the rising from the dead should mean.
11 And they asked him, saying, Why say the scribes that Elias must first come?
12 And he answered and told them, Elias verily cometh first, and restoreth all things; and how it is written of the Son of man, that he must suffer many things, and be set at nought.
13 But I say unto you, That Elias is indeed come, and they have done unto him whatsoever they listed, as it is written of him.
Luke 9:26(KJV) For whosoever shall be ashamed of me and of my words, of him shall the Son of man be ashamed, when he shall come in his own glory, and in his Father’s, and of the holy angels.
Luke 9:27(KJV) But I tell you of a truth, there be some standing here, which shall not taste of death, till they see the kingdom of God.
Luke 9:28-36(KJV) And it came to pass about an eight days after these sayings, he took Peter and John and James, and went up into a mountain to pray.
29 And as he prayed, the fashion of his countenance was altered, and his raiment was white and glistering.
30 And, behold, there talked with him two men, which were Moses and Elias:
31 Who appeared in glory, and spake of his decease which he should accomplish at Jerusalem.
32 But Peter and they that were with him were heavy with sleep: and when they were awake, they saw his glory, and the two men that stood with him.
33 And it came to pass, as they departed from him, Peter said unto Jesus, Master, it is good for us to be here: and let us make three tabernacles; one for thee, and one for Moses, and one for Elias: not knowing what he said.
34 While he thus spake, there came a cloud, and overshadowed them: and they feared as they entered into the cloud.
35 And there came a voice out of the cloud, saying, This is my beloved Son: hear him.
36 And when the voice was past, Jesus was found alone. And they kept it close, and told no man in those days any of those things which they had seen.
His word holds true as Peter, James and John all saw this before they died. Hopes this helps to clear some of this up.