I won’t be surprised if Manhattan prices do drop in the next few years, but I also strongly believe that the future of New York City continues to be bright. Homo sapiens are a social species; almost all of what we know we learn from each other. Dense cities, like New York, succeed when they take advantage of this fundamental aspect of our humanity. They thrive by enabling us to connect with each other, which then promotes learning and innovation. The current downturn will only increase the returns to being smart, and you get smart by hanging around smart people. As long as New York continues to attract and connect those people, the city will continue to thrive.
This supports a point some commenters made in response to one of my posts on the housing bubble, although Glaeser is crediting demand rather than tight supply.