The launches themselves can be made roughly neutral by producing the methane and LOX from the atmosphere using solar power. For an hourly cadence, that would require as much solar as a third of all US installed commercial solar, but the US is already adding that much every few years, and accelerating, so it doesn't seem impossible. That's best-case, of course, but given that, all the combustion products would balance out propellant generation.
Reentry of dead satellites and other debris does seem like it's eventually going to be more of an issue, so that will be something to work on.
I wouldn't count on any warp drive breakthroughs, potentially ever, but the whole solar system is still out there for living and industrial space.
Even if resources don't evaporiate in our atmosphere, you need to send up a lot of resources like metals.
We are so so so far away of mining resources on other planets/moons than earth, setting this up now is just crazy though.
And lets think crazy wild: in 20 years we send up enough stuff like machines and resources to start mining and setting things up, to do what? I love scifi but it has to reach some kind of goal.
Reentry of dead satellites and other debris does seem like it's eventually going to be more of an issue, so that will be something to work on.
I wouldn't count on any warp drive breakthroughs, potentially ever, but the whole solar system is still out there for living and industrial space.