I believe that getting to settlements in space does not require any new technology- we can do it using expendable chemical rockets. At least getting to orbit which is half to anywhere.
The problem is lack traffic volume and is mainly economic problem related to this.
I believe that finding minable deposit of water on the Moon would be an important step towards increasing demand for cheap launches.
Another piece of the puzzle (about as important) is developing sub-orbitor vehicles for space tourism/rocket racing.
Another way of approaching it, and is somewhat *related to* lunar water mining is the govt buying water test payloads (lowers launch costs by encouraging new launchers being built, and could provide water in orbit which could be "mined").
This is how I think we can get to space colonies in the quickest, cheapest, and fastest way I know of.
Oh, and there is also my idea of a pipelauncher- basically could be looked at as a better launchpad. Allows you to use ocean as launch range, is cheap, and adds some speed to rocket at launch.