Tech investment is, unfortunately, not a zero-sum game. Every dollar that doesn't go into a Silicon Valley tech company is not guaranteed to go into a tech company elsewhere.
So yeah, the failure of SF/SV will probably mean an increase in tech investment in other cities, but ultimately I don't think there's a chance in hell we'll break even. It will be a huge net loss for the tech industry as a whole.
Not to mention there isn't really a strong SF/Bay Area alternative when it comes to tech. I know Boston/Tel Aviv/Berlin/Toronto (add Montreal, Waterloo, NYC, Austin, and Seattle to the list for more completeness) like to hang up banners proclaiming themselves to be just like Silicon Valley, but let's be honest, the scale difference is enormous. None of the above listed cities are even close to being able to assume Silicon Valley's mantle.
Even as someone who no longer lives in the area, who has no interest in returning to the area, the loss of the SF/Bay Area's status as the de facto tech capital of the world will have enormous negative repercussions.