If all those low density areas in SF were converted to high density, SF could grow a lot and housing issues could be plaited temporally (years?) but after a while it be the same thing, where there's more demand than supply.
Personally, I think having single-family housing inside a city is a waste of space but a city full of 30 story buildings usually is not very pretty. I like the Eixample, were streets are wide and buildings just the right size so there is plenty of sunlight, airflow and all that. Obviously if I were an owner of a single-family home in SF I would be against of converting my quiet, low-density neighborhood into all high-rise.
Tricky problem to solve.