How one understands Matthew's words depends a lot on how one understands the word "generation." I think we can be misled if we insist that "generation" means "an age (i.e. the time ordinarily occupied by each successive generation), a space of 30-33 years." That is only ONE way in which the word is used in the New Testament. Indeed, the Online Greek Lexicon, a part of "The Online Bible" which is actually a Bible program, gives 4 distinct meanings of the word:
Please notice definition 2. People of the same stock, could refer to a nation, in this case the nation of Israel, the descendants of Jacob.1074 γενεα genea ghen-eh-ah’
AV-generation 37, time 2, age 2, nation 1; 42
1) fathered, birth, nativity
2) that which has been begotten, men of the same stock, a family
2a) the several ranks of natural descent, the successive members of a genealogy
2b) metaph. a group of men very like each other in endowments, pursuits, character
2b1) esp. in a bad sense, a perverse nation
3) the whole multitude of men living at the same time
4) an age (i.e. the time ordinarily occupied by each successive generation), a space of 30-33 years
Notice according to the above, the King James translates the word once as "nation" (Philippians 2:15)
It seems peculiar that the blood of all God's prophets from the beginning would be charged to the people of that generation in the sense of a period of 30 years or so. It seems to make better sense that it would be charged to all Israelites of all times who rejected God and/or His Messiah.
(Luke 11:49-51 ESV) Therefore also the Wisdom of God said, ‘I will send them prophets and apostles, some of whom they will kill and persecute,’ so that the blood of all the prophets, shed from the foundation of the world, may be charged against this generation, from the blood of Abel to the blood of Zechariah, who perished between the altar and the sanctuary. Yes, I tell you, it will be required of this generation.
I suggest that "this generation will not pass away until all these things take place" refers to the people of Israel. There have been many attempts to exterminate them throughout the centuries, but none have succeeded. This understanding does not force Christ's predictions to refer to the events surrounding 70 A.D.