We read that Avraham and Lot, from Shem and Yaphet no doubt, came into the land of their "brother" Canaan. Cham was in the South, up till the land of the Philistim and in the North and East, Nineve and Bavel. And Avraham received his prophetic dream, "your offspring will be aliens in a land not their own", but "afterwards they shall leave with great wealth."
The perush is clear. The sons of Avraham, the Jewish nation, will go into the Galut, to all the nations of the world, against their will. There, in the Galut, the nation will absorb "holy sparks", unvoluntarily, more or less. Afterwards, the nation will leave the Galut, with all the sparks, a great wealth. Unvoluntarily, to a large degree.
In the land of Canaan, in the Land that was promised to Abraham, a holy nation will thus arise, a reverse Bavel, many languages becoming one, in Zion. This is the awesome method of HaShem, His Will of old, and it is against the will of the "spark-less" nations of the world.
This perush is long indeed. It does not consider Galut Mitzraim as the fulfillment of Avraham's dream. Galut Mitzraim is only the first of all the Galuyot that had to be. L'chatchilah. The reason is that Mitzraim may have been the superpower of the day, but mankind is much older and way bigger. Only when all have contributed their holy sparks, the end, of the dream, is there.
For the details about the timing, see this, and references therein, and this, or this.
