In the meantime, many Texas cities: http://time.com/80005/why-texas-is-our-future are building tons of affordable housing, even as superficially liberal cities like Seattle legislate it out of existence.
Yes, it's very slow going. But this is also a case of every time we "win," another 5,000 people show up with mountains of cash who can outbid everyone else in the region. Seattle is very popular as a place to live so we're trying to outrun both normal demand and the demand for housing that doesn't cost multiple thousands of dollars. It is a tough slog.
(By the way, Seattle has some of the most far-reaching renter protections in the state. Rent control is barred by state law but Seattle requires landlords to do a lot of things, provide a lot of notice, and limit rent increases a lot more drastically than any of our surrounding suburbs. Oh, and those suburbs aren't exactly building their own capacity, either. Good luck getting a large multi-residence project approved on Mercer Island or in Bellevue outside of the downtown core. Redmond is right out. Shoreline and Renton are doing better than most; Shoreline even pushed back against its own citizens to say "look, light rail stations deserve density around them so we're doing it, sorry nearby single-family homeowners.")
Maybe more of those would come in handy here in San Francisco too!
Probably more impactful in terms of population numbers is the similar "apartment block over water" which popped up in Seattle a few decades back and are still around. ~5 stories and over water is a lot more people than a row of houseboats.
[1] https://www.google.com/maps/place/Floating+Homes+Association...
It been a few years since I heard that though, it may be incorrect or outdated.