Once our space infrastructure is sufficient mature, there will be people who will head
out into the galaxy regardless of what is out there, whether we know something or not.

There will be those who want to find other intelligences in the galaxy to become
enlightened, spread the Word of God, take their resources, etc. It won't matter if we
know if any ETI exist by then or not, or if they are friendly or not. People will want to
encounter them in person.

Others will set sail for the Milky Way to get their own turf, to get rich, to escape
corrupt politicial systems, to found their own religion, to escape being arrested, maybe
even try to conquer the galaxy for themselves.

Unless humans radically change by the time we can do some sort of interstellar flight,
I forsee the first "astronauts" beyond the Sol system to be nothing like the astronauts
we have orbiting in the ISS right now. Just like in the American West, where the ones
who really settled the place were not always the best and brightest, but the most
ambitious and determined.

Look out, galaxy, here comes humanity in all its messy glory!