The historical age obviously produced a second generation of giants, whatever that mechanism was. It is interesting that the giants had a very keen sense of geopolitics and their relation to the coming messiah. Though one may find them scattered all over the globe, nestled in myth and lore and occassionally in the archaeological record, they were clustered in the ancient Levant. They positioned themselves carefully, and either subjogated or alligned with peoples of the region. Why? Their primary mission was to thwart God's plan and corrupt humanity, and they had no way of knowing when messiah would come, only that God would redeem mankind through the Jews. Accordingly, they situated themselves in the greatest numbers in the ancient Near East.
In Matthew 24:37, Jesus tells us that the conditions of his return will mirror those of Noah's day. That includes the Nephilim--the giants. If their acumen for geopolitics was astute in the past, should we expect anything different at the return of the Son of Man? The simple answer is "No." The Nephilim will return. Be watchful.