This is my take on a number of different footnotes from the Ignatius Catholic Study Bible.
The coming of the son of man refers to (Dan 7:13). This refers to Christ ascension and coronation when he is given the kingdom. Then sitting at the right hand of the Father, God decrees the destruction of all Christ's enemies (Ps 110:1) Linked to this "initial" coming is the visitation of destruction upon unfaithful Jerusalem in A.D. 70. (which was earthly evidence of Christ's vindication that his disciples witnessed). And heaven continues to deal with Christ's enemies. So there was a "coming" within the generation of the living apostles but not his Second Coming in glory. Instead, the vistitation of destruction is a prelude or pre-figurement of his Second Coming. First century events point to (look forward to) his Second coming.
Jesus left the temple area and was going away, when his disciples approached him to point out the temple buildings. He said to them in reply, "You see all these things, do you not? Amen, I say to you, there will not be left here a stone upon another stone that will not be thrown down." As he was sitting on the Mount of Olives, the disciples approached him privately and said, "Tell us, when will this happen, and what sign will there be of your coming, and of the end of the age?" (Mt 24:1-3)
"Learn a lesson from the fig tree. When its branch becomes tender and sprouts leaves, you know that summer is near. In the same way, when you see all these things, know that he is near, at the gates. Amen, I say to you, this generation will not pass away until all these things have taken place. (Mt 24:32-34)