If everyone builds luxury condos then there is too much competition and the price declines, builders will seek to build more profitable units. So long as "affordable housing" is above cost, then eventually it will be the most attractive new good to provide the market.

It will take a long time for the process to work though, because it takes years to build things, plus a year for Leases to cycle. In the meantime I imagine NIMBYs will say "see? nothing improved".