Ugh, please no. The real problem is that startups can't decide to open up shop somewhere else, like Pleasanton or Napa. Somewhere that's just as accessible to all the VCs and conferences but not so short on housing.
I don't want mega city. I'm sure a lot of people who have made the Silicon Valley their home for many years agree. It's just the young crowd who has to live in apartments anyway that think more mega Apartment buildings would be great. I completely refuse to live in SF because of the density and turn down any job based in SF automatically.