If you are referring to verses like
Ex. 34:7,
Num. 14:18,
Deut. 5:9, your interpretation of "third and fourth generation" as meaning three and four "ages" completely misses the purpose behind these verses. God punishes three or four generations to ensure that the sinner never lives long enough to see a descendant who is not paying for his sins, so that
he will wail every day of his potentially long life at the visible consequences of his sin. (Aquinas saw this. “The text adds, ‘to the third and fourth generation,’ because men are wont to live long enough to see the third and fourth generation.”
Summa Theologica Part II Q. 87 Art. 8.)
Whatever. My understanding is that the visitation of the iniquities of the fathers is still being visited upon their children and the Children's today during the fourth age of their existence. Since the iniquities of the fathers occurring over the first two ages of the existence of the Israelites, only began being visited upon the fathers' children and the children's children during the third and the fourth ages I do not believe that these verses are referring to descendant generation like you are suggesting but rather to ages.
Exodus 20:5: - 5 You shall not bow down to them or worship them; for I, the LORD your God, am a jealous God, visiting the iniquity of the fathers on their children to the third and fourth generations/ages of those who hate Me,
Exodus 34:7: - 7 maintaining loving devotion to a thousand generations,a
forgiving iniquity, transgression, and sin.
Yet He will by no means leave the guilty unpunished;
He will visit the iniquity of the fathers
on their children and grandchildren
to the third and fourth generations/ages.”
Numbers 14:18: - 18‘The LORD is slow to anger and abounding in loving devotion,a forgiving iniquity and transgression. Yet He will by no means leave the guilty unpunished; He will visit the iniquity of the fathers upon their children to the third and fourth generation/ages.’
Deuteronomy 5:9: - 9 You shall not bow down to them or worship them; for I, the LORD your God, am a jealous God, visiting the iniquity of the fathers on their children to the third and fourth generations/ages of those who hate Me,
Hosea 6:1-3 presents a picture that confirms that Israel's idolatrous worship has been visited upon the fathers' children and the Children's children during the third and fourth day of the Lord which has the same duration as an Age.
Hosea 6:1-3 speaks of God inclining His ears towards the Israelites after two days of the Lord walking contrary to Israel and Israel walking contrary to God.
You are using the same reason as others have presented as to why Genesis 15:16 is not referring to 1948 AD.
Shalom