I'm not sure where do you get the idea that people aging 18-30 care about those specific things. I assume Pew will have some statistics about interests and priorities for these ages but I wouldn't be surprised if those are not the main worries of the generation. Yes, urban living is on the rise and with it some of these list item will rise too (density, night life, high speed internet, public transportation...) but this is a trend that will affect most mayor cities in the US.

My guess? The "next valley" will be highly decentralized and a lot of big cities will act as innovation hubs.

Oh and remember that the valley happened well before the flock of young people to SF. Lot of factors played in, including the presence of well established semiconductor companies whose employees were far from the stereotype you are describing.