They will probably be sold to rental management companies (of which there will be a whole bunch) or like liquid-property-investment startups like https://bricklane.com/
The thing that prevents new construction in many areas is laws designed to "preserve the character of the neighborhood". Homeowners/investors have an incentive to push for these laws to keep housing prices high. However, if they actually own a diversified asset that can grow with new construction by adding new properties, then that incentive is reduced.