9:1 And he said to them, “Truly I tell you, there are some standing here who will not taste death until they see the kingdom of God having come in power.”
It is now perfectly clear to me that Mark 9:1 is not meant as a comforting address to the faithful, but instead as a stark prediction/warning to the unfaithful.
There is a big difference, then, in "seeing" the kingdom having come in power, and being part of the kingdom having come in power! It depends on whether you have been unfaithful, i.e. not "denying oneself", or faithful and denying yourself, even through humiliation in this life. You don't want to be the ones on the outside "seeing" the kingdom when it has been established!
Of this I am thoroughly convinced. Further, I think that Jesus is not just addressing anyone who does not embrace the Christian truth, but specifically those who, like the example of Peter just before (8:33), recognize Jesus as the messiah, but won't embrace the harsh life of "denying oneself", which can include dying by execution, like Jesus himself.
Thus: In Mark 8:38 Jesus is talking about those who recognize Jesus as the messiah, as their ruler, and as such wishes to be "behind" him, i.e. "follow" him as their king (and not just "follow" him as a teacher, which has been the meaning of this concept in the narrative up until now), but who find shame in the their ruler's humiliation, i.e. his rejection, torture and death, which will soon be a reality. And these 'Christians', who belong to "this adulturous and faithless generation", will be rejected by this humiliated ruler, when he is going to appear in his glory.
So there is intended a juxtaposition here in this verse of the 'son of man', meaning the glorious ruler messiah, in his presently visible humilated form on the one hand, and the 'son of man' in his eventually revealed glorious form. It takes the spiritual vision that comes from faith to 'see' his glory now in his humiliated form.
That is why Mark is speaking about the "shame" of these wannabe followers of the messiah and the "glory" of 'the son of man'. Because the shamefulness of these people comes from the element of Jesus' humiliation, that he is supposed to be the king, but he is instead humiliated, and so must his subjects be. Therefore there is a direct connection between the words "ashamed" and "glory".
Because "ashamed" has to do with the present humiliated form of the 'son of man', or messiah as the followers understand it. When they see the messiah in the form of the glorious, heavenly figure spoken of in Dan 7, then they will understand that they should not have been ashamed after all. At the present, because of their unfaith, they can't 'see' that he is the king, the messiah, or, they don't believe it, but eventually they are going to see his glory. Of course, then it's too late!
Then they will realise, that it is true what Jesus has just said: "The one who wishes to save his life [in the flesh] will lose it [at the judgement, not living on in a glorious incorruptible body], and the one who loses his life [in the flesh] because of me and the gospel will save it [at the judgement, living on in a glorious incorruptible body]" (8:35)
They didn't want to follow the messiah because of the shame of the humiliation that goes with it, "denying oneself" (8:34), and so they are going to save their asses from humiliation, even humiliation to the point of death. So some of them will live to see the messiah when he actually comes in his royal glory, in his glorious incorruptible resurrected body, and then they'll think "oh, crap!" And even though they had escaped death, unlike the martyrs, they are going to taste death now! Or rather, they are going to face judgement, like all other humans, and the faitful who took upon them the shameful humiliation in the flesh and even died, will acquire new glorious bodies by the power of God's force, his "dynamis".
This concept, God's "force" ("δυναμις") is generally in the NT used to describe the concrete force by which resurrection takes place, meaning the concrete creation of the new bodies with which the faithful will be clothed to enter the kingdom of God. Therefore when the judgement comes, the unfaithful will be destroyed, but the faithful will receive these glorious eternally living bodies created through God's "dynamis", just like he creates every form of life through this "dynamis". And when all the faithful have been clothed with their bodies, then they will constitute the "kingdom of God having come in force ("dynamis")".
And that is when the unfaithful are going to witness this scene, the faithful clothed in their eternally living resurrected glorious bodies! At this point the faithful who had suffered humiliation in the flesh can now really enjoy how their unfaithful fellow humans realize that they were wrong and the faithful were right and rub it in their faces! And then the unfaithful are taken into the dungeon for destruction, i.e. "losing his life", which Jesus has just warned about in the verses preceeding 8:38-9:1. The unfaithful had thought to themselves that they saved their life, but those of them who have not died from old age or in some other way when the son of man and the judgement comes, will indeed "lose" their life now. The second death.
So they may think that they will not "taste death", because they escape death in the flesh, but after the judgement, when they see all the resurreced faithful clothed in their glorious bodies, when "they see the kingdom of God having come in force", then they will taste death after all.
And this whole thing is exactly what Jesus talks about in 9:1:
The whole emphasis is on "until". They will not taste death "until"! Meaning, then they will taste death.
And then comes the Transfiguration where some of the disciples are lucky to witness the resurrection before time. They get to "see" what the unfaithful will only "see" when it is too late. The same thing in 13:27 and 14:62. The unfaithful will "see" it when it's too late, and realize it when it's too late, when instead they should have been able to 'see' it now with spiritual vision that is given through faith.