This is vaticinium ex eventu. So it practically proves that the author wrote this Gospel after 70 AD. He wanted Jesus to proclaim a prophecy in which Jerusalem will be destroyed and then after some gentile domain over the city, it would be restored, occupied and administered again by the Jews. And of course, it tells us that early christians of the first century, after 70 AD, were preaching a messianic early kingdom centered in Jerusalem rebuilt (Acts 1:6-7). This expectation was still in force until the end of the second century, because greek christians as justin and Irenaeus believed in it.
Jerusalem is now mostly occupied by Israel again, and the nation does not believe in Jesus as the Messiah. So, we should recognize that the Gentile Times, as defined in Luke 21, practically ended in 1948 (not in 1914), but the world continues as such.