Urban cycling is in, along with old-esque forms of bicycles that are practical and comfortable for the average person to ride in the city. And hipster track-bike-wannabees speeds are on the way out, I think.
I'm in favor of anything that get's more people on bikes, especially if it means they're riding bikes instead of driving cars. At the same time, I'm suspicious and uncomfortable with the "fashion" element of this urban bike fad. First, I've always associated fashion with shallowness, since it focuses on appearance rather than merit, and snobbery, since fashionable things cost more simply because they're fashionable. Second, like any fad, if someone buys a bike for fashion, it may spend a lot of time in the apartment or garage once the "look what I bought" photos are posted, tweeted whatever. But then, the same thing happened during the 70s bike boom--everyone had to have a 10-speed, riding it was purely optional.
But if the urban cycling craze can be the entry drug for more people to get on bikes, I'll overlook the parts I find distasteful.