Clearly, no one can know what the future will bring and how our descendants will be living in decades and centuries from now. They might be experiencing clean and uncrowded residential areas with amazing high tech to enable a drudge free lifestyle. They might have an affluent societies similar to what is portrayed in TV shows like Star-Trek or The Jetsons. Alternatively, they might endure an impoverished, overcrowded and gloomy future.
Of course it's possible that cities of the future will be built atop boats due to the melting of the ice caps. These vessels would be a combination of factories, fisheries and residences. They could become independent polities that trade with each other and maybe engage in conflicts.
And, you can visualize independent factory city-states that exists on land, as in the movie Mortal Engines.