Technically we can confidently say we're the only ones living here, because we've defined the word "life" and what it means.

And we tend to define life in a very terrestrially and DNA-specific way, despite we don't mention it explicitly.

My favorite are the pointless arguments about whether viruses are alive or not. As if "it's alive" is some objective property of a thing. It's not. It's a word we made up.

Maybe the Moon is conscious for all we know. We know almost nothing.

As for effective communication and interaction with aliens, it'll most likely require cybernetics and genetic engineering.

The idea humans will colonize the universe is very naive. We're Earthlings. We're extremely fragile outside very specific conditions on this very specific planet. To live successfully outside we'll have to change a lot.

Sure, technically whatever that ends up being we can still call "humans" but it won't look like humans do right now, that's for sure.