No generational ships until we have a few different habitats in orbit and on the moon.

Tons of stuff to work out for a trip of that length.

But in all reality the generational ships are going to be scientific arks that are gathering data and sending it back to earth. But probes would be more feasible, and cheaper.

One often considered possibility, is we figure out how to go ftl, but we need to have a portal at each end. So we'd need to send a ship to build one at the destination. But at the point we're doing that, it's likely going to be a fuily automated ship.

Human bodies and lifespan, just dont fit with our current tech and space travel.