If we accept the assumption that FTL travel and communication is absolutly impossible (I don't, but you obviously don't want to argue about it.
) then I highly doubt that we as a species will ever travel beyond our solar system. The distances are just too great. And what reason would we have to go? There is plenty of things right here in our solar system to explore and plenty or room for colonies. Why spend decades or centuries travelling to another system when you can spend months or years and stay close by.
Even if you could expand the human life span to thousands of years, who wants to spend hundreds of years in the void between the stars? Very boring. And it would be an astronomical risk to go that far out with no hope of rescue if your ship broke down. And it hard to keep a complex mechanical device like a spaceship functioning that long while carrying everything with you you need to make repairs.
Perhaps if we make long distance contact with some alien race we'll want to meet them up close. But the distances would be so great it just wouldn't be practical.