Eric Klinenberg, in Going Solo, notes that half of Manhattan households are made up of people living alone. New York is certainly the capital of solo living in this country. But they are not really representative of future trends elsewhere.
Many young people go to New York to try to make it big, or just to experience the cosmopolitan life - for awhile. Then they pick a more realistic option elsewhere, or marry and move to the suburbs, or run through their trust fund or parental subsidy.
I think the fact that Klinenberg is a professor at New York University in Greenwich Village gives him a distorted view of how common, or sustainable, solo living is.