Regardless, if there are fewer people then if each person buys more crap then the pyramid can be maintained.
Going forward, if the world population does level out we will see even greater attempts to get people to surround themselves with pricier crap.
Well, crony capitalism certainly does - that's why our elites' priorities are "all immigration - all the time." Just get the potential consumers and taxpayers in the door, and never mind who they are or where they came from.