I agree that in the absence of the context of what was supposed to occur during "this generation" that it might have been presumed to be those of Jesus' generation. But two issues exist here:
1) "This generation" was to experience all the signs given, including the prophesied desolating of "Judea" a one-time event that was clearly prophesied to occur during the "end times." So, certainly no indication there that would occur during the immediate common generation of Jesus' time, say within the next 40-80 years.
2) The second thing is, whether if Jesus was making a crytic reference in relation to his earlier statement in Matthew where he says:
MATTHEW 16:28 " 28 Truly I say to YOU that there are some of those standing here that will not taste death at all until first they see the Son of man coming in his kingdom.”
The early Christians fell into two classes; those who would end up dying and needing a resurrection before the Lord's day and those who would actually "survive" down to the Lord's day over a 1900-year period. So TECHNICALLY some of those of Jesus' generation could say that they would not pass away until these things came. It's almost the same statement, since part of the signs included in "this generation" was the second coming.
John and Paul were two we know of who did not die throughout the ages before Christ arrived. At 1 Thess 4:15 we can clearly see Paul placing himself in the "surviving" group, those who would be not die until Christ came, but clearly enough in the past that all those not in this "living-surviving" group would be expected to have died out completely.
Note how Paul is answering a doctrinal issue with regard to the two distinct groups, which is if those who "survive" down to the Lord's day would receive their prize before those needing to be resurrected:
15 For this is what we tell YOU by Jehovah’s word, thatwe the living who survive to the presence of the Lord shall in no way precede those who have fallen asleep [in death]; 16 because the Lord himself will descend from heaven with a commanding call, with an archangel’s voice and with God’s trumpet, and those who are dead in union with Christ will rise first. 17 Afterward we the living who are surviving will, together with them, be caught away in clouds to meet the Lord in the air; and thus we shall always be with [the] Lord.
This merely confirms that the first resurrection will occur first back into the flesh so that everyone anointed in Christ at the time of the second coming will all be in the flesh together for a period of time before they ALL, together get their heavenly bodies. Those no group will precede the other to their reward.
Just as a background note, per the Bible 1/10th of those of the Bride Class must be natural Jews and must comprise 12,000 from each tribe. The entire number 1,440,000. (See Isa 6:13)
13 And there will still be in it a tenth, and it must again become something for burning down, like a big tree and like a massive tree in which, when there is a cutting down [of them], there is a stump; a holy seed will be the stump of it.”
This means that 144K are natural Jews, 12,000 from each tribe and the other 90% are grafted in gentiles to the symbolic king-priest olive tree.
But there's a huge logistical problem here, obviously. How can you guarantee and fulfill that 12,000 from each of the 12 tribes will make up the root in later times over 1900 years later? Especially after the destruction of Jerusalem in 73 BCE would keeping up the genealogies be difficult. One solution would be to allow some who could prove their lineage during the time of Jesus be selected to live down through the ages for 1900 years like Paul and John and then at some point, depending upon how many were selected, marry into the modern population so that in say several generations each person could have up to a million descendants to choose from for the 12,000 required from each tribe. That would fulfill the technical letter of the prophesy and promise.
But having noted that, that means it really doesn't matter if Jesus meant some who were alive during his day would not die before the second coming, not to occur until 2520 years after thef all of Jerusalem.
So you can HAVE IT EITEHR WAY. "This generation" could be an 80-year generation reference (Ps. 90:10) during which all these signs would occur beginning with the very first sign, which was a world war (i.e. kingdom vs kingdom, nations vs nation); OR it could be another reference that some of Jesus' generation would not die at all until he arrived, even though he was not scheduled to arrive for over 1900 years.
So either way it works with a modern date for the second coming. Biblically speaking.
JCanon