Building up SF or SV is not the solution, High Speed Rail is the solution. Get on a HSR train, travel 20 - 40 miles out of the city in under 30 minutes. People would still have access to SF, SV and the jobs but would be scattered upwards of 40 - 60 miles from SF, SV. It also fixes NIMBY; you can either have HSR or be surrounded by large apartment blocks.