Actually, that's not the only theory of post-scarcity. Another one, which I subscribe to, is that there's nearly limitless resources in the universe and that our problems are productivity, accessibility, and the time it takes to access and produce what we need from them (energy included). By the time we have access to the stars of the universe and the planets surrounding them in some capacity, we'll have so many resources at our disposal that the notion of scarcity will seem silly. Scarcity will only be a real issue once we're so populous that we literally dominate the universe and are suffering from overpopulation, and before then we may well find something that maps onto your post-scarcity theory which would be pretty awesome.
Though still, until the time described, the issue isn't scarcity itself but rather productivity, accessibility and the time needed for both. This is why we're more prosperous in freer societies. People tend to be more productive and the access of resources is less impeded by political bodies, not to mention that the time it takes to produce is reduced when you don't have to jump through regulatory hoops. If we're worried that free-reign capitalism will exhaust our resources before we can access the rest of the universe, all I can really point out is that our options are either stifling ourselves and not making it out there anyways, or running the free market risk since only there will productivity be high enough for us to get there. SpaceX is a very good example of exactly this, all the way down to the having to jump through bureaucratic hoops to get into and retain a place in the space travel market in the first place. And yet, for all these restrictions, it's already made some amazing innovations and reduced the cost of space travel drastically.