Why would we expect the Lord to perform his acts of power and glory just once — be it in the past or the future? What good does that do all the other generations?
It seems to me that all prophecy ultimately finds its accomplishment in Christ internally and personally, as opposed to externally and historically. Even the cross must be received, and each follower must bear it as Jesus said (in the same chapter as the “son of man” passage in Matthew 16).
So, with that in mind, consider this “son of man” passage in light of the immediate context found in Matthew 16: martyrdom.
The theme of self-sacrifice is developed consistently through the second half of the chapter, with the pivotal passage just a few verses prior to our “son of man” reference — 25 For whosoever will save his life shall lose it: and whosoever will lose his life for my sake shall find it.
Therefore, we might see Jesus saying “There are some standing here who will be laying down their lives for my sake (and, Peter, you are one). However, fear not, because you will not have perished until you see me coming for you in my kingdom, to your great delight.” etc..
For support of this idea, take a look at Stephen’s martyrdom in Acts 7:
54 When they heard these things, they were cut to the heart, and they gnashed on him with their teeth. 55 But he, being full of the Holy Ghost, looked up stedfastly into heaven, and saw the glory of God, and Jesus standing on the right hand of God, 56 And said, Behold, I see the heavens opened, and the Son of man standing on the right hand of God. 57 Then they cried out with a loud voice, and stopped their ears, and ran upon him with one accord, 58 And cast him out of the city, and stoned him: and the witnesses laid down their clothes at a young man’s feet, whose name was Saul”
Might this not be a perfect example of the “son of man” passage being fulfilled in Stephen? This method also makes more sense of the “henceforth” sayings regarding the coming of the son, due to the continual acts of martyrdom upon local Christians (26:64 Jesus saith unto him, Thou hast said: nevertheless I say unto you, Hereafter shall ye see the Son of man sitting on the right hand of power, and coming in the clouds of heaven.)
Clearly, AD70 figures into the imagery, as you pointed out, but as nothing more than a visible, external show of these very personal revelations (per Israel’s entire role as visible schoolmaster of invisible things). The True Israel/Christian flight to Pella at the last minute might be seen as the figure of the deliverance prior to the fall.
At any rate, perhaps we have vastly underestimated the significance of martyrdom in its coloration of New Testament eschatology. For support of this contention, specifically noting Paul, check out one of his eschatological “time texts” :
“the time.. is at hand” - II Tim 4:6
(now, without the dots)
“the time of my departure is at hand.”
http://www.jesuscreed.org/?p=3313
http://preteristheresy.blogspot.com/2008/02/todd-dennis-how-full-preterism-fails.html