>>12497124I reckon it'll be an ionic/nuclear tug, a spacecraft with extremely high ISP engines (almost 1000 at least, possibly as high as multiple thousands) that permanently stays in space, can attach to other spacecraft, and is refuelled by whatever it's tugging.
These tugs could also be outfitted with other stuff that has no reason to leave orbit, and would be a pain for many companies to develop independently. For example, anything intended to improve quality of life for humans in transit. These tugs could even be centrifugal habitats, and the only part of the spacecraft occupied by humans during transit, with the spacecraft they're attached to only serving to move stuff in and out of orbit.
With lots of competitors in the space industry, being able to provide a service that makes everyone's operations a lot cheaper could make you enormously successful.
Personally, I don't think this is something SpaceX would do, in fact SpaceX is probably what will cause another company to try this approach. If no one can beat SpaceX as a launch provider, they could still make a killing by assisting underdog launch providers, and the resulting specialisation of individual companies could lead to a more efficient operation than SpaceX can achieve.
