Not everybody wants to leave Earth
When Gerard O'Neil suggested his free-floating space colonies as a refuge
and new way to start over for Native Americans, their general response was:
"Great, first you kick us off our land, now you want to kick us off the planet!"
There will be enough adventerous and disgruntled groups who will want to get
off this ball of rock to make space colonization a reality. It's the nature of life
to have parts of it break off to seek new territory due to conflicts and such.
And humans are no less a part of this plan.