It is true that in the coming generations, we'll learn things we don't even dream today (barring global catastrophe and so forth). But that's why I also included the "unless we develop FTL or teleportation" line...because without either one of those the logistics of moving the kind of mass (including sufficient humans) needed to start a colony to a viable planet become close to impossible.

But again, you're right that we do have a tendency to surprise ourselves with finding ways to do things. I hope we never lose that skill.