SF prices still (if you believe the fundamentals outlined in the NYT article - which I do) still has at least 20%+ to fall in a short order... and no reason to have returns greater than inflation for the next decade. Makes no sense to buy as long as rents are relatively cheap.
My bet - lock in a ridiculously low lease in 12 months and then count yourself lucky that SF has tough laws for landlords as inflation kicks in as rents run up.