We are experiencing the opposite phenomena here on the SF peninsula. Slums are disappearing, and neighborhoods are gentrifying with more upscale residents.
Who knows. After the stock market crashed in 2008, it was business as usual in SF and the market rebounded to newer heights. SF does not rely on the stock market for it's existence.
Ever hear the saying "don't put all your eggs in one basket"? The economy is diverse here. It's not just computer tech. There is finance & banking, medical tech, shipping, manufacturing, educational institutions, robotics, etc. on and on. Any one of them fails, the others will keep the economy going. One of the biggest growing areas here is medical biotech. Whole neighborhoods have been created around new biotech centers. So it doesn't look like the economy shows any signs of slowing here. That's one of the main reasons for an influx of tech talent coming here (as well as homeless and illegals looking for a free ride).