Rabbi Frand in The Difference Between The Two Tochachas cites Rav Soloveitchik as saying that the consolation appears in Parsha Nitzavim rather than immediately after the tochacha in Ki Savo.
Rav Yosha Baer Soloveitchik, z”l, asks: Why the difference? Rav Yosha
Baer answers that in fact the Tochacha in Ki Savo also ends with
consolation… except the consolation only appears in Parshas Netzavim:
“And it shall come to pass, when all these things are come upon you,
the blessing and the curse, that I have presented before you – then
you will take it to your heart among all the nations where Hashem,
your G-d, has dispersed you. And you will return unto Hashem, your
G-d, and listen to His voice, according to everything that I command
you today, you and your children, with all your heart and all your
soul. [Devorim 30:1-2] The consolation is that at the end of all the
punishment and suffering, the Jewish people will do Teshuva [repent]
and return to G-d.
This still leaves the question as to why the delay until Nitzavim. R
explains that the Rav Soloveitchik explains that the tochacha in
Bechukosai foretells the destruction of the first Bais Hamikdash, whose
exile was foretold to be 70 years. The destruction of the Second
Temple, foretold in Ki Savo caused our current exile, which will end
at some point, but we cannot know when that will be.
But the question can still be asked: Why is it that in the Tochacha in
Devorim, there is a pause and we have to “wait for the consolation”,
so to speak, while in the Tochacha in Bechukosai, the consolation
comes immediately? Rav Soloveitchik answers this question by
explaining that there is a fundamental difference between the two
Tochachas. The Ramba”n says that the Tochacha in Bechukosai foretells
and refers to the period of the destruction of the First Bais
HaMikdash and the exile from the Land of Israel at that time. The
Tochacha foretold in Ki Savo refers to the destruction of the Second
Bais HaMikdash and the exile that occurred at that time. The
Destruction of the First Bais HaMikdash and the Babylonian exile which
followed it had a prophesized finite end to it. The prophets foretold
that the people would be in exile for 70 years and indeed following
this 70 year period, the Jews were given permission to return to the
Land of Israel (where they eventually rebuilt the Bais HaMikdash).
Therefore, it makes sense that the Tochacha which foretells the
Babylonian Exile features the consolation in close proximity to the
end of the pasukim of chastisement.
As we now know, we do not know of a specified date for the redemption
from the Destruction of the Second Bais HaMikdash. We have now been in
this exile for close to 2000 years! However, there will be an end to
this exile. As the Rambam writes in the Laws of Repentance: “Israel
will only be redeemed through repentance. The prophets have already
promised that the Jews will repent at the end of their exile and
immediately thereafter they will be redeemed, as it is written…” (and
then the Rambam quotes the pasuk in this week’s parsha) “…And it will
be that when all these things come upon you… you will return unto
Hashem your G-d.”
When will that occur? We do not know, but it will come. This is
precisely why the consolation does not immediately follow the Tochacha
here in Devorim. We need to wait. We need to wait until we return to
the L-rd our G-d. We are going to be in the mess in which we find
ourselves until we do Teshuva.
This is the difference between the two Tochachas. In the first, we
just had to wait a (relatively) short time. When the clock struck 70,
we were able to go home. The current exile is not like that.
Eventually, we will get out of it because “in the end Israel will
repent and immediately thereafter they will be redeemed” but we do not
know when that is going to happen.