Then the Lord said to him, “Know for certain that for four hundred years your descendants will be strangers in a country not their own and that they will be enslaved and mistreated there.
And then in v. 16
In the fourth generation your descendants will come back here, for the sin of the Amorites has not yet reached its full measure.
Is there a connection between the four hundred years sojourn in Egypt and the fourth generation returning to Canaan? This question has been inspired by this question. There Phil suggests a provocative idea that the four generations are actually the equivalent of four hundred years, since in the biblical framework a generation (or more specifically an Abrahmic generation) is thought to be the equivalent of a hundred years. Phil believes that this explains how the four generation prophecy has been fulfilled, while I take issue with it and offer another solution. But then it struck me that it may actually be the other way around, i.e., if Phil is right in suggesting that a generation is a hundred years, then is it possible that the four hundred years is actually modeled after the four generations, i.e., that the four hundred years of Egyptian bondage is another expression of the four-generations-in-bondage prophecy? I'm inclined to think that it's modeled this way and not vice versa, since the fourth generation motif is a common motif in the bible, and can also be found in the ten commandments, so it makes sense that if there is any modeling after, that the four generations prophecy (i.e. that the iniquity of the Amorites has not reached full measure until the fourth generation) would precede the four hundred years prophecy.
This may possibly resolve the age old Egyptian sojourn chronology problem, since if four hundred years only meant four generations then the fact that it was less than four hundred literal years (but four literal generations) should not pose much of a problem, since the four hundred years were never meant to be taken literally, but as another expression of the four generation prophecy which was indeed fulfilled, see here. But I'm getting ahead of myself.
My question is has such a connection ever been explored? Is there evidence to suggest that a generation in the bible is the equivalent of a hundred years, and is it plausible that the four hundred years were understood by the biblical authors as four generations and nothing more?
The only problem I can see here is that understood this way, the four generations prophecy would in a way undermine the four hundred years prophecy. Since according to v. 16, the fourth generation is already returning to the land, whereas according to v. 13 the Israelites would be in bondage for four hundred years, i.e., four complete generations. This problem is actually very similar to the problem I raise with Phil's answer here. There are ways to resolve this (and the problem with Phil's answer), but I'm leaving this question open for now, awaiting the feedback of the community.