Without artificial gravity of some type and a propulsion system that reaches speeds in the 100,000 mi/sec range, we are going nowhere. Currently artificial gravity is sci fi and top velocity is 10 mi/sec. But with billions of years, we have time. lol
Then we are doomed.
(Actually, I feel that as soon as someone figures out how to make money off of space travel, the exodus will begin and, even if we have to use generation ships, we’ll get off Earth)
Artificial gravity isn’t sci-fi, it’s an ancient principle. Tie a bucket onto a rope and swing it around your head. Centripetal force isn’t new. Just have to make the rotating piece big enough in diameter to keep the angular velocity down and keep people from getting motion sickness.