If we can figure out how to get to other stars relatively easily, through new discoveries in physics, then we wont need to waste our time developing inhospitable planets, but can search around for more hospitable ones...Earthlike ones. Much would depend on just how rare a planet like Earth is.
But I suppose we need to crawl before we can walk, and walk before we can run. Just overcoming the problems of gravity would be enough to get us started.
Tuor
According to Ward and Brownlee, "Rare Earth," earth is probably unique. I would expect that every settlement from here on out will be totally constructed using the best technology. Earth is both the cradle of Man and the mother's breast. It is time to be weaned; it is past time to start solid food.