Will "Aliens don't exist" be the "The world is flat" of the future?

Could be. I guess this one is a little trickier than proving the world is spherical because humans had the ability to do that before but were too frightened, as where we're actively searching for other forms of life but haven't found any. Unless you trust the supposed diatom algae residue found on that asteroid.

lol actually I know this wasn't your point but the civilizations that were big on seafaring had a good understanding of the earths curvature; further from shore you lose sight of objects from the ground up.

Maybe we humans are alien to this planet. Earth, the land ruled by dinosaurs. We invade it, demolish their existence, make base, and call it our planet. In that case, we could have relatives in other galaxies.

I believe so, although I don't think humanity will make long enough to make contact

The odds that they exist somewhere is actually pretty good.

possibly...now with just life or intelligent life?

Probably

I'm a alien

tell me more about those aliens you speak of

I think "aliens dont exist" will be the "pro-vaccinations" of the future, obviously correct, but with a growing movement of idiots who cant help but believe the first thing they hear.