re: Colonies
There's another factor. We've talked about it before on this board: the urge to spread. It's in our BIOS. What drove the peopling of this planet will, if/when possible, drive the peopling of others, and the spaces between.
It will happen when it's time to, but it will happen, as surely as Beringia was crossed by H. sap.
My personal favorite among SF futures, regarding humans in the greater Solar System, is the background for much of Varley's early work (see, for instance, The Ophiuchi Hotline).
