Until recently, there were CA cities so hostile to landlords that I'd say it would be crazy to be a landlord in those cities. Now the State of CA is making the worst of those cities' ordinances state law. The state of CA is basically anti-landlord, so the chances of a lot more rental housing coming on the market are near zero, IMO.
BTW, Johnny2X2X's claim that rich NIMBYs block the building of new housing has some validity in places like SF, where space to build is highly limited. And some of the NIMBYs are the anti-"gentrification" activists. But in areas like Oakland or Silicon Valley, there is buildable space that is well away from rich NIMBYs, and it is anti-developer regs, fees, and take-aways that discourage building new housing. OTOH, Johnny2X2X is correct that Enviro-regs, laws that enable Enviros to increase the delays and costs of building a development, and "open space preserves" that close large tracts of land do obstruct building housing.