Many question whether Luke 21:20-24 occurred in 70 A.D. or is it still a future prophecy. I believe Luke’s version of the Olivet Discourse in Luke 21 is primarily a future event and coincides with the timing of Daniel’s 70th week (Daniel 9:27).
The prediction of the destruction of Jerusalem in 70 A.D. was given by Jesus in Luke 13:34-35 & 19:41-44;
34 "O Jerusalem, Jerusalem, you who kill the prophets and stone those sent to you, how often I have longed to gather your children together, as a hen gathers her chicks under her wings, but you were not willing!
35 Look, your house is left to you desolate. I tell you, you will not see me again until you say, 'Blessed is he who comes in the name of the Lord.'"
41 As he approached Jerusalem and saw the city, he wept over it
42 and said, "If you, even you, had only known on this day what would bring you peace--but now it is hidden from your eyes.
43 The days will come upon you when your enemies will build an embankment against you and encircle you and hem you in on every side.
44 They will dash you to the ground, you and the children within your walls. They will not leave one stone on another, because you did not recognize the time of God's coming to you."
The Triumphal entry into Jerusalem occurred one week before Jesus' resurrection and at that time Jesus describes the prophetic judgment coming upon Jerusalem. Why judgment? Israel did not recognize “the time of God's visitation” (1st Coming).
If Luke's prophecy is future, then a future temple must be rebuilt. There are three N.T. verses supporting a third, future “Tribulation Temple.” (Matthew 24:15, 2 Thessalonians 2:1-4 and Revelation 11:1-2).
Matthew 24:15 (NIV)
15 "So when you see standing in the holy place 'the abomination that causes desolation,' spoken of through the prophet Daniel--let the reader understand--
2 Thessalonians 2:1-4 (NIV)
1 Concerning the coming of our Lord Jesus Christ and our being gathered to him, we ask you, brothers,
2 not to become easily unsettled or alarmed by some prophecy, report or letter supposed to have come from us, saying that the day of the Lord has already come.
3 Don't let anyone deceive you in any way, for that day will not come until the rebellion occurs and the man of lawlessness is revealed, the man doomed to destruction.
4 He will oppose and will exalt himself over everything that is called God or is worshiped, so that he sets himself up in God's temple, proclaiming himself to be God.
Revelation 11:1-2 (NIV)
1 I was given a reed like a measuring rod and was told, "Go and measure the temple of God and the altar, and count the worshipers there.
2 But exclude the outer court; do not measure it, because it has been given to the Gentiles. They will trample on the holy city for 42 months.
Some form of the Third Temple will be rebuilt and daily sacrifices will offered. However, at midpoint of Daniel's 70th week, the Abomination of Desolation occurs and the Antichrist will take his seat in the temple and proclaim himself God. The Temple will serve as his throne for the second 3 ½ years. Ultimately, this temple will be destroyed by a great earthquake(s) at the Second Coming of Messiah. (See Ezekiel 38:19, Zechariah 14:4, 6-9; Isaiah 29:1-8; Revelation 6:12, 8:5, 11:13, 16:18-21).