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Me I say..
Launch: Orbital elevators using carbon nanotube cable
Engines: NTRs, solar sails or STRs, or fusion rockets
Where: Luna, maybe Mars, Asteroids for sure
Why: Incentive. When we get orbital elvators, launch costs will be far cheaper. Ground to geostationary is predicted to cost as little as a few hundred dollars per person. This would make building anything in space relatively cheap, because it removes launch cost restrictions. I think we'll see tourist destinations on the moon and in geostationary orbit relatively early. We'll also see asteroid mining thanks to the massive quantities of things like precious metals. Belt colonies might open up as a result. Fusion power generation will make mining He-3 from gas-giants very profitable (10 tonnes, say, enough to power north america for 1 month, and worth 200 billion dollars as fuel / 16 million per KG as material).