Political conditions have improved dramatically in the past 500 years. We've gone from Monarchies to Democracy's, from an institution where everyone is subject to the whims of the leaders to a government of law.
If we have a similarly 'lackluster' change in the next 500 years, then I think progress will be just fine.
Furthermore a lot of the barrier is technological, and we've had huge technological advances even in the last 10 years. If that continues, eventually the price of spacecraft will come down so far that exploration is viable.