The white hot growth in Brooklyn has slowed down to the extent that Queens and *the Bronx* both added more people between 2015 and 2016. Manhattan isn't growing super fast either, at least not compared to earlier this decade
Besides the new buildings in Hudson Yards, there isn't really anywhere to add more people here, lol. I wouldn't be surprised if NY County starts losing pop at some point soon, since residential space is going to have to be taken over by office space, and there's only so many more skyscrapers we can build.