There will be no literal physical third temple that will be built. Well there may be (end times deception) but that is not what scripture is talking about.
The third temple doctrine comes from 2 Thessalonians 2:4: "Who opposes and exalts himself above all that is called God, or that is worshipped; so that he as God sits in the temple of God, showing himself that he is God."
That verse is indeed speaking of the coming man of sin, the false messiah, the antichrist. But it is not speaking of a literal temple.
"Though the image is drawn from the Jewish temple, we may say with some confidence that St. Paul did not expect the antichrist as a prose fact to take his seat in that edifice. Neither is the metaphor to be pressed into a mere synonym of "the Church" (1Corinthians 3:17). The words, so far need not necessarily mean that the Man of Sin will make special claims upon the Christian community as such. Rather, the whole phrase, "taking his seat in the temple of God," is a poetical or prophetical description of usurping divine prerogatives generally: not the prerogatives of the true God alone, but whatever prerogatives have been offered to anything "called God." Though the prophecy might be fulfilled without any symbolical act (e.g., of assuming any material throne), yet the spontaneousness ("himself") and the openness ("showing himself") seem so essentially parts of the prophecy as of necessity to imply that the Man of Sin will make formal claim to occupy that central seat in men's minds and aspirations which is acknowledged to be due to God alone. The formal making of this claim seems to be identical with the apocalypse of the Man of Sin, the act by which he is manifested or revealed." -Ellicott commentary on 2 Thessalonians 2:4.
When the antichrist is revealed, everyone will see him and know of him. All those that are not the true elect of God will be deceived by the false messiah, the antichrist, into believing that he really is the messiah, that he really is God. In their minds, which is what the temple of God in this scripture is referring to, the minds of men and women, in their minds the antichrist will actually be God to them.
So there is no end time 7 year tribulation period, and there is no literal physical third temple. What are we looking for? Were looking for the revealing of the false messiah, the antichrist. He will deceive many into believing that he is the messiah, that he is God. God's true elect, those that strictly obey His word, His commandments, His will in this life, that have made a sacrifice of their lives to devote it to God, to live for God and not themselves, these true Christians, these wise virgins (parable reference), will be able to discern the false messiah when he comes.