Until someone can design a way to travel faster than light, mankind is not going anywhere. Even if it was possible to put a human into cryosleep without brain damage. Would you trust a bit of tech not to breakdown after 10 years never mind 1000. If you built ships big enough for a people to live and breed on, by the time the future generation got anywhere they wouldn't have a clue how to live off the land they found. That's if some space bacteria didn't kill them in their first breath.