In its extreme form, it would also mean that the final coming of Christ referred to in Matthew chapter 24 and Second Thessalonians chapter 1 already occurred during the apostolic age.
Historicalism teaches that most Biblical predictions would be fulfilled only some considerable time after they were given — fulfilled either once or repeatedly during the whole course of world history. Thus Historicalists regard the promised “seed” in the Protevangelium of Genesis 3:15 as referring not principally to that generation’s Abel and Seth etc., but principally to Christ and His Christians (only to be born many centuries later).