You could feasibly quadruple the population if you wanted to, I guess my question is to why? It wouldn't decrease rent appreciably, and you would have to move out to daly city to raise your family in something other than an apartment.
You could do all this building and ruin the atmosphere of the lower half of the city just for Amazon, Salesforce and whatever other software companies are still downtown to move to some desert and have the rents drop back down to normal ranges.