Yes. I do see our moon becoming something like that instead. (:
The space elevator idea is really genius though, and will speed things up dramatically too. I think the order of operations to get to the 3 stages described in the OP (in other words our progress from now to 2150 A.D.) would be something like this:
- Build reusable rockets (reduces cost of space missions by 100 fold)
- Build space elevator (commercial spaceflight is a reality)
- First human landings on mars / exploration of the terrain.
- A.I. develop. Manufacturing costs dramatically decrease for humanity.
- Advances are made in interplanetary Spaceships. Commercial cruises to planets.
- Nuclear fusion energy is mastered, humanity now has a near-inexhaustible power supply.
1 - This one is already being worked on by SpaceX. It may be ready within 5 years, or 10 at most. And has already been used by NASA on contract.
approx ~ year 2020
2 - I hear Google has plans for this already. I'm assuming it'd be made out of carbon-fiber. This is certainly an inescapable necessary step forward. This could theoretically be done by 2020 if funds were available. If not then after step 4 (see below).
approx ~ year 2020 or 2030
3 - Several groups are in the works to get there by 2022-2025. The famous Mars One, and Mars Semi-Direct are two that come to mind.
approx ~ year 2023
4 - Ray Kurzweil predicts sentient A.I. will develop around 2029. We already have less-than-human-level A.I. working many of our machines and that will continue to grow, and we'll have manual labor become obsolete (as per GodofOrder's essay)
approx ~ year 2030+
5 - The first interplanetary missions will be cramped and uncomfortable, like the one to Mars. But once the space elevator is up, within a decade or two production of costs will be so low that comfortable cruises to mars/venus/jupiter will be possible. Our designs will get better and we'll be able to design the ships needed to perform the venus-to-mars oxygen transfer missions, and the ice-asteroid missions. Assuming the space elevator is built by 2040, then this will happen by 2060.
approx ~ year 2050+
6 - This is an unknown to me, but with the aide of the superintelligence of A.I. emerging around 2030, I suspect we might have this down by 2060 as well, if not sooner.
approx ~ year 2060+
So optimistically we could start terraforming mars by 2060-2070, but politics and other things will likely drag some of these things out, still I can't see them taking longer than by 2150 A.D. to get started on Mars.