I don't think there is any chance of humans leaving Earth unless the human body can be re engineered to handle being in places with different environmental conditions including atmosphere, radiation, gravitational forces and so forth. We are better off doing all we can to clean up and fix up our own planet. It is incredibly beautifully and unique. In regards to exiting planet, for generations, the best we can probably do is send out a small number of people to explore universe but, besides knowledge, I would not expect a huge return on that.