OK, after reading the last Act of SM and Seiya mentioning a few things, it occurs to me that now that life is peaceful on Earth, for sure peaceful this time, the Sailor Senshi know that there's lots of intelligent life in the rest of the galaxy. Additionally, Usagi restored the Kingdom on the Moon back in the Dark Kingdom arc, and at the end of Stars, the other planets in the Solar System are supposed to be capable of sustaining life (somehow. Someway. Still not sure how you could exactly live on a gas planet with 2.5x the gravity of Earth, or on a planet with 95% C02 and temperatures of 460 Celcius, or on a planet with lethal iron dust).
So what if this gets noticed by scientists, NASA, astronauts, etc (except for the Moon Kingdom since magic hid it or something)? Findings are released to the public. Usagi decides to lift the magical veil that hides the Moon Kingdom and tells all to the world.
I imagine you'd have trouble from many religious fundamentalists and extremists at first, but after, once mankind turns to develop new space technology again, Earth launches forth several colonies, and establishes contact with the other races, with Crystal Tokyo becoming the center of the human race. Far different than original timeline Crystal Tokyo, where they didn't have all the encounters with beings from other planets.