Well we would basically need to be able to effectively colonize a nearer celestial body, then be able to refine and miniaturized THAT tech, as well as refine and miniaturized the tech used in the transport ship so that we could build something massive and efficient enough to house multiple generations of people. And for a generation ship to work ot would have to accommodate both a large number and handle a wide variance of growth, as birthrates become less predictable the smaller the gene pool gets.

Personally I would think if we could develop that tech, we should just live on space stations.