It might take millions of years. It might take as long to colonize mars as for conditions on Earth to change and resemble Mars, and for life to evolve the proper adaptations. Only then would the amount of technology required to survive on Mars (or the other planets) be minimized.

I saw a show recently called "The Future Is Wild" in which it was predicted that in 300 million years the Earth's continents would once again merge into a supercontinent, and this might create extremely hot dry desert-like conditions across most of the land area. Life in this hypothetical future might be more closely adapted to conditions on Mars, Mercury, and several moons with minimal technology support.

Of course 300 million years is the timeline for natural selection. Maybe we can speed things up a bit. There's plenty of sci-fi speculating that bio-engineering is the way to go. Might as well use all that human genome project research for something.