This [objective] is achieved through "Beis Rabbeinu" [Our Rebbe's House] in the lower hemisphere, from which light goes out to all the world, to make the whole world (until the furthermost corner of the world) into the land of Israel. This is the concept that "In the future the land of Israel will extend into all the lands," and "In the future, Yerushalayim will extend over all the land of Israel."
For then there will be established a connection between all the synagogues and study halls throughout the entire world and the Beis HaMikdash. [This will occur] in the true and complete Redemption through our righteous Moshiach, the leader of the generation, who is the Moshiach (the Redeemer of Israel) of the generation. Further, and this is also essential, he is the leader of the Torah of Chassidus, since through the spreading outward ("when your wellsprings spread forth," until there is nothing beyond, to all corners of the world) is achieved the coming of the king Moshiach.
Therefore the greatness of "Beis Rabbeinu" can be understood. It is the essential "Temple in microcosm" of the final exile, "that the Temple traveled and settled there." Therefore, it is the actual place of the Temple of the future; not only that, but the future Temple will be revealed there, and from there return to Yerushalayim (as cross-references).
