I don't see San Francisco turning into Detroit. It's more likely to follow Pittsburgh's path, and Pittsburgh isn't a bad place to live these days (but it's far from a star city).
What you missed was the twenty years where Pittsburgh turned into Detroit. Losing all of your industry followed by 60% of your population does that do a city. As a Pittsburgher, it's a good city with ambitions to be great, but it took a generation to get there.
As a former Pittsburgher (now Detroiter) The cities are culturally very different, even if economically their paths were similar.
Pittsburghers really believed in their city, even through the tough economic times. If anything I miss about Pittsburgh it would be that. An older generation of suburban Detroiters would simply have no second thoughts if the City of Detroit burned to the ground. That was one of the most jaw dropping things about moving here, the lackadaisical attitude towards the state of the city among the older generation.
Although IME it actually seems like the tech industry in Detroit is humming along quite nicely. The auto industry is back again and there's a resurgence of startup and entrepreneurial spirit around these parts. My company is hiring like mad.
However I feel like the local economy is struggling to find people who will actually move here. Even if there are perfectly livable areas in the region, very few people have a good mental image when you say "I'm moving to Detroit!"
