Yes, eventually people will have to learn to do with less, as the earth resources dwindle.
I'm not sure about that aspect as driving force for less availability. Every atom 'used' is still here, it's a matter of getting even better at rearranging them.
No easy feat, yet all it really needs is energy and people ingenuity, we're getting much better at that all the time. And with a great nuclear fusion reactor in the sky we're not running out of energy anytime soon.
Demographics can be a thing, although we already reached peak child on the inflow side. The biggest trend to fight (besides black swams like epidemics and meteors) is on the outflow side: aging badly.
Bunch of dementing, frail and useless elderly (of which I would be one) supported by dwindling youth can throw us off the deep end. Unclear how that will evolve, Japan and Germany are giving us the 'best' sneak peek right now and in the coming years.
The only unsolvable issue is less land per person with each person. Before that really becomes a problem we'll need to go x3 or x5 though. Still a ways off whatever growth or aging scenarios prevails.