The GR"A teaches different teachings on Yeshayahu 60:22 (B'Itah Achishenah) and Chazal's take on it from Bavli Sanhedrin chapter 11.
Zachu - Moshiach ben YosefIn the hagahot of the GR"A on the Rambam's halachot on Moshiach, a teaching is brought to resolve the disagreement between the Rambam and the Raavad.
The Rambam holds that the world will continue as normal, whereas the Raavad holds that the world will shift to a miraculous nature. The GR"A there says that these are both the words of the Living G-d.He goes on to explain: Tana D'vei Eliyahu teaches that the years 4000-6000 are 2000 years of Moshiach. The GR"A explains, if we merit, from the year 4000 onward we can have Moshiach ben Yosef come and rule over us. Moshiach ben Yosef is from the side of Din, so whether or not he comes is dependent on our actions alone. How early in this time period he arrives is dependent on how much zechut we have.
Moshiach ben David, on the other hand, is from the side of Chesed, so this cannot be merited, as this is against the concept of Chesed. When Hashem decides to give us this gift, and we cannot change this.
So to summarize, if we merit it, Moshiach ben Yosef can come at any time between the year 4000 and the time of the advent of Moshiach ben David.
In the GR"A's peirush to Sifra Ditzniuta, chapter 5, the GR"A boldly states that not only does he know the final Keitz B'Itah, but also he says how to figure it out yourself. Of course he does not make it easy. A logical inference limits it merely to 5751-5834 (the 10th hour, in which Adam HaRishon sinned), whereas the GR"A is quoted elsewhere that the Geulah can really be defined down to a single year. The implication from the way he writes there is that he is going by the classic understanding of Zachu/Lo Zachu.
The Middle Path in Kol HaTor
In Kol HaTor, an interesting problem is raised regarding the interpretation of Chazal of B'Itah Achishenah. The thing is, Chazal's drash is not according to any sort of pshat. Let's look at the pasuk again:
The smallest will be for a thousand, and the young lad for a mighty nation, I am Hashem, in its time, I will hasten it.
So the real "pshat" is that at a certain point, the time of the Geulah will be moved up. When will that be? When the first pasuk is fulfilled, that we will reach the level of a thousand (ad v'lo bichlal, 999) and a mighty nation.
This takes us back to the drash on the 4 paths of Geulah that I wrote about a few months back. We have the ability to choose the way the Geulah comes. We can arrive at the level of Teshuvah required and then we will be redeemed (the Rambam says in Hilchot Teshuvah that this would be immediate), Hashem will compel us to do Teshuvah, we can wait for the last moment, or we can do the actions of the Atchalta in the role of Moshiach ben Yosef.
Therefore the "pshat", if you would pardon the term, is as follows:
If we do our efforts here from below and advance on the path that is laid out before us, fulfilling the goals of Moshiach ben Yosef, then we will arrive at level of 999, and at that point, the Geulah will be sped up. Then the Moed of the Keitz will come towards us instead of vice versa.
Please note on the word "pshat" that I used here. The GR"A is quoted as saying in Even Shleimah that until you understand the sod of a pasuk, you cannot be certain that you understand the pshat. The two must match or the pshat is wrong.
It turns out that all four paths converge in the end.
- The Teshuvah we need at this time to merit the Geulah is both within our personal space (the daled amot of halachah) as well on the national level, of us doing Teshuvah here in Eretz Yisrael.
- The Diaspora will be eliminated one way or the other in the near future, by our desire or by way of refuge. I am starting to believe that there will be less obvious warnings than the last time the Diaspora was in danger.
- Hashem is pushing Am Yisrael closer and closer to the Keitz Meguleh, forcing our hand on a regular basis towards Tikkun (Why is it so hard to establish a state for the Arabs here?)
- The Keitz Mechuseh, the final appointed time, is rapidly approaching. The Keitz is not at the end of the 10th hour.