It is eternal: As everything Moshe made is eternal. The Talmud states in (Sotah 9a) with regard to Moshe, as the Master said: When the first Temple was built, the Tent of Meeting was sequestered, including its boards, its clasps, and its bars, and its pillars, and its sockets. The Gemara asks: Where is it sequestered? Rav Chisda says that Avimi says: Beneath the tunnels of the Sanctuary. The significance of this is that each of the Botei Mikdosh and Mishkons all have some unique virtues. Each one expresses a unique way in which Hashem is revealed to the world. In the third and final Beis Hamikdosh there will be the completion and perfection of this revelation, this will be expressed in the fact that the third Beis Hamikdosh will include all of the virtues of the previous Botei Mikdosh and Mishkons.
