Yaakov wanted to reveal the ketz

In the beginning of parshat Vaychi, Rashi writes:

And Jacob lived Why is this section [completely] closed? Because, as soon as our father Jacob passed away, the eyes and the heart of Israel were “closed,” (i.e., it became “dark” for them) because of the misery of the slavery, for they (the Egyptians) commenced to subjugate them. Another explanation: That he (Jacob) attempted to reveal the End [of the exile] to his sons, but it was“closed off” (concealed) from him. [This appears] in Gen. Rabbah (91:1).

What is the meaning of this idea that he wanted to reveal the ketz? I believe that the answer lies three perakim later:

א וַיִּקְרָא יַעֲקֹב, אֶל-בָּנָיו; וַיֹּאמֶר, הֵאָסְפוּ וְאַגִּידָה לָכֶם, אֵת אֲשֶׁר-יִקְרָא אֶתְכֶם, בְּאַחֲרִית הַיָּמִים.

1 And Jacob called unto his sons, and said: 'Gather yourselves together, that I may tell you that which shall befall you in the end of days.

Such that he promises to tell them what happens in the acharit hayamim, in the end of days. But what follows might be classified as blessings, or might be classified as predictions. Commentators are divided on it. After all, how can what is said to Reuven and Shimon be considered a blessing?

Aside from that, Shadal explains that on a peshat level, beacharit hayamim just means in later days, but for everyone else aside from Shadal, are these statements of Yaakov really about apocalyptic times? So Rashi, e.g., says:

and I will tell you, etc. He attempted to reveal the End, but the Shechinah withdrew from him. So he began to say other things. — [from Pesachim 56a, Gen. Rabbah 89:5]

So this explanation of the parsha setumah was not just pulled out of Rashi's streimel (or the streimel of the author of the midrash). There are other textual cues filling it the specifics of the midrash, just as is the case for almost any midrash.

Yet if we read the rest of Rashi's commentary, he explains Yaakov's words as prophecy, just not end-of-days prophecy.

On the other hand, we already have a Biblical pattern of fathers blessing their children beterem their death. And we have Yaakov blessing Ephraim and Menashe. And even within Yaakov's speech here, we have:

כה מֵאֵל אָבִיךָ וְיַעְזְרֶךָּ, וְאֵת שַׁדַּי וִיבָרְכֶךָּ, בִּרְכֹת שָׁמַיִם מֵעָל, בִּרְכֹת תְּהוֹם רֹבֶצֶת תָּחַת; בִּרְכֹת שָׁדַיִם, וָרָחַם.	25 Even by the God of thy father, who shall help thee, and by the Almighty, who shall bless thee, with blessings of heaven above, blessings of the deep that coucheth beneath, blessings of the breasts, and of the womb.
כו בִּרְכֹת אָבִיךָ, גָּבְרוּ עַל-בִּרְכֹת הוֹרַי, עַד-תַּאֲוַת, גִּבְעֹת עוֹלָם; תִּהְיֶיןָ לְרֹאשׁ יוֹסֵף, וּלְקָדְקֹד נְזִיר אֶחָיו. {פ}	26 The blessings of thy father are mighty beyond the blessings of my progenitors unto the utmost bound of the everlasting hills; they shall be on the head of Joseph, and on the crown of the head of the prince among his brethren.

So anyway, according to the aforementioned midrash, Yaakov wanted to reveal to them the ketz. But how did Yaakov know the ketz? This is a question posed by Daat Zekeinim miBaalei haTosafot. After all, he is not a mystical blogger who can skillfully interpret sefer Daniel, or Zohar, or Ramchal. So how in the world would Yaakov Avinu know the ketz?!

Zaat Zekeinim has an answer. He suggests that Yaakov counted the rungs of the ladder in his dream. That is, according to one midrash, he was dreaming about the various exiles.

The "problem" with this is that if I recall the midrash correctly, Yaakov specifically did not know how much the angel of Edom ascended. To cite Midrash Tanchuma:

דא"ר שמואל בר נחמן:
מלמד, שהראה לו הקב"ה לאבינו יעקב:
שרה של בבל עולה שבעין עוקים ויורד,
ושל מדי חמישים ושנים,
ושל יון מאה ויורד,
ושל אדום עלה ולא ידע כמה. באותה שעה נתיירא יעקב אבינו ואמר: שמא לזה אין לו ירידה?!
א"ל הקדוש ברוך הוא: (ירמיה ל) ואתה אל תירא עבדי יעקב ואל תחת ישראל, כביכול אפילו אתה רואהו עולה אצלי, משם אני מורידו, שנאמר: (עובדיה א) אם תגביה כנשר ואם בין כוכבים שים קנך, משם אורידך נאם ה'.

Hashem thus assures him that there will be an end, though Yaakov does not know what it is. So it would seem a stretch to claim that Yaakov now knew when the ketz was.

Indeed, I would say that the very point of the midrash cited by Rashi later about the Shechina withdrawing from him is that he would tell them, via prophecy, when the ketz was. Not that he was able to tell them at any time. (Though this might not have been how Daat Zekeinim understood the midrash.)

Daat Zekeinim also brings down a charming midrash about a conversation about being able to reveal to them the ketz. I have seen different versions which have different conversants -- either Hashem conversing with Yaakov (Daat Zekeinim), or Yaakov conversing with his sons (Baal HaTurim, same page, same link). Yaakov was wondering why the Shechina departed. According to Daat Zekeinim, Yaakov noted to Hashem that there was no letters chet or tav in all the letters of their name. Hashem replied that neither were the letters kuf or tzadi.

As an interesting aside, we see here that this midrash spelled chet, sin, without a final aleph. This plays into this issue about the gematria of egoz and not eating egozim on Rosh Hashana, discussed here, and then in terms of this midrash, here.

According to Baal HaTurim, Yaakov's sons make the point of having no chet in their names, and the rejoinder about lacking ketz in their names is Yaakovs. A pity, because we could have made a nice consistent pattern, connecting the conversants with the belief that Yaakov did or did not personally know the ketz, or whether this knowledge was held by Hakadosh Baruch Hu.

A separate point of consideration is which ketz? It could mean the final, apocalyptic end of days, or it could mean the ketz of galut Mitzrayim. Even if we read the Tanchuma like me, Yaakov could have seen the sar of Egypt ascending, so as to know the ketz. Of course, that midrash only discusses the 4 exiles, and so does not discuss galut Mitzrayim. Plus anyway, Daat Zekeinim himself proposes (in the same page linked above) that the acharit hayamim refers to the exile in Egypt for 430 years -- motivated by the heh hayidiya, and that otherwise it would have to say beacharit yamim besof yemei olam. But then he considers it means the final end-of-days, and in that context, discusses the ketz, as above.