In an article for Vayakhel-Pekudai (Hachodesh) 5773, Rabbi Cherki notes that the Third Temple will be a permanent edifice, as the world acheives final redemption.
Because the word "mishkan" appears twice in succession ("These are the accounts of the Tabernacle, the Tabernacle of testimony" [Exodus 38:21]), the sages predicted that in the future it would be treated like a short-term "deposit" which would eventually be destroyed because of the sins of the nation (the word mishkan might be related to mashkon, a loan guarantee). This teaches us that the appearance of the Shechina (the Divine Presence) below, in this world, is a weak effect which does not have the strength to remain constant throughout all history. This phenomenon is related to the fact that the Tabernacle represents the appearance of the holy presence, rooted as it is in infinity, within the limitations of the real world.
The presence of the holy world in the realm of nature is in some ways the planting of a foreign object within the real world. And since nature resists any element that is foreign to it, as long as history proceeds along natural lines every Temple that is built will eventually be destroyed. This state of affairs will continue until the construction of the Third Temple, when the world and the Temple will be perfectly matched. Then the entire world will be raised up to the status of the Temple, as is written by our sages: "Jerusalem will extend from Gaat to the gates of Damascus" [Shir Hashirim Rabba 7:3], and the Land of Israel will grow to encompass the entire world. Similarly, the Temple will take up the whole space of Jerusalem, as is implied by Zechariah (14:21).
When holiness begins to spread into the world, the Temple will no longer be destroyed. We may think of history as being planned as a sequence of eras, where the Temple exists during some and is destroyed during others, and this interaction between the separate holy world and nature leads to progress in the world.
In this week's Torah portion, the phrase "just as G-d commanded Moshe" appears eighteen times. This can give us an indication of how the Temple helps to bring about the perfection of creation. In the description of creation in Genesis, the phrase "And G-d said" appears nine times. It is true that "the world was created with ten declarations" [Avot 5:1], but the first one, the word Bereishit ("in the beginning"), is ambiguous. The created world can only absorb nine of the declarations. It is written, "The actions of righteous people are greater than the actions pertaining to heaven and the earth" [Ketuvot 5a]. With respect to creation, it is written, "My hand made the foundations of the earth and My right hand measured the heavens" [Isaiah 48:13]. This seems to imply that the Holy One, Blessed be He, built the world using only one hand. But with respect to the Temple it is written, "The Temple, G-d - Your hands built it" [Exodus 15:17] – with two hands. In the Temple there is a link between the hand which built the heavens and the hand which built the earth, and this shows the unity of all creation. And that is why for the Tabernacle the number of declarations is double – and the phrase "just as G-d commanded Moshe" appears eighteen times. (Source: Rabbi Shlomo Goren.)