It's possible, but it depends on the city. Yesterday's luxury apartments become today's affordable apartments if yesterday's luxury apartment tenants move into

It's possible, but it depends on the city. Yesterday's luxury apartments become today's affordable apartments if yesterday's luxury apartment tenants move into today's new luxury apartments, leaving their old luxury apartments vacant with upper-class buyers to replace them. But in some cities, like New York and San Francisco, many of the new luxury apartments are being bought up by foreign investors who keep the apartment empty, or being bought up by rich outsiders who are moving into the city for the first time. So the increase in housing supply at the upper end of the market is only inducing additional demand and keeping prices high, instead of working against existing demand and either lowering prices or improving value (i.e. sticky prices which stay high, but buyers can now get a nicer apartment for the same cost). Such "filtering" is definitely possible, but you'd have to find out a way to restrict immigration and market speculation to make it a reality.