The sicha that was said on Parshas Vayakhel, 5752, was never properly edited due to the stroke of 27 Adar. However, the overview (“rashei dvorim”) that was written up and presented to the Rebbe after Shabbos was, uncharacteristically, marked up by the Rebbe. Thus, it passed before the Rebbe, and what needed correction was corrected.
In this overview of the sicha, it says:
…we see in recent years how there has been a “vayakhel” (gathering) in the simple meaning of the word — the ingathering of the exiles (“kibbutz goliyos”) of bnei Yisroel from the entire world, who are going up to Eretz Hakodesh. This aliyah is incomparable to those that once were in the previous generations. [To point out that Rabboseinu Nessienu were not in the Holy Land, not even for a visit, and even the trip taken by the Friedicker Rebbe was because he was unable to visit the resting places of his predecessors in Rostov, Lubavitch, and the like].
For all the prior years of the Rebbe’s leadership, the Rebbe was adamant in saying that Jews going to Israel is not the ingathering of the exiles (“kibbutz goliyos”), because the ingathering of the exiles must be done by Moshiach.
We can say that what is new is that now the aliyah–the Jews who were leaving the former Soviet Union, in particular–came about through Moshiach and thus it does fulfill the requirement of Kibbutz Goliyos.
This expression “Kibbutz Goliyos” is of monumental significance, because this is one of the requirements of Moshiach to be identified as “certainly Moshiach”. As the Rambam says, if he builds the Mikdash in its place and ingathers the exiles we know with certainty that he is Moshiach.
More than that, the Rebbe explains in the Kuntres “Beis Rabbeinu sh’b’Bavel” that the Rambam writes that Moshiach “builds the Mikdash in its place”, which can be read as “in his place”, referring to the “mikdash me’at” (small mikdash) in the time of golus before the Geulah. How “literally” to understand the Rebbe’s explanation there is strengthened by our sicha about Kibbutz Goliyos, because the Rebbe explains elsewhere (the Chassidic discourse “Gadol Yehiyeh Kavod Habayis Hazeh…”):
the Redemption, (the ingathering of the exiles,) will take place after building the Beis HaMikdash…this dimension comes about through the Third Beis HaMikdash…For the Third Beis HaMikdash, includes all the influences and qualities that will later be revealed.
Meaning that the Ingathering of the Exiles is fueled by the 3rd Beis Hamikdash, and if the Rebbe can say that it has begun then there must be a Mikdash built that is bringing it about. So 770 becomes not only the place where the Mikdash will be revealed in the future, but in fact it is now, as per the halacha of the Rambam, the Beis Hamidash in his place (the place of Moshiach before the Geulah)!