current trends seem to be toward giant, self-contained communities within skyscrapers. meh.
I'd like to see more of nature incorporated into cities, to lessen the carbon footprint and keep wildlife from being pushed to the margins. This is necessary for the survival of the human race and the planet, as cities are continually expanding and will take up more and more of the planet's surface in the coming decades. The paradigm of cities and manmade communities existing as isolated islands distinct from the surrounding nature is an old and outdated model that will not lend itself toward a sustainable, eco-friendly future.
BBC - Future - Why we need to bring nature back into cities
In addition to the eco-friendly aspects, I seem to remember reading a study or studies suggesting how increased exposure to nature is good for our own mental wellbeing. So this is not just a win for animal life, but for the human animal.
I'd also like to see giant floating ocean cities that harness wind, hydraulic and solar energy.
Floating Cities, No Longer Science Fiction, Begin to Take Shape - The New York Times
World's first floating city set for 2020 in Pacific Ocean | Daily Mail Online
My only worry for these floating cities is that, just like the self-contained skyscraper communities, they may become havens for the wealthy whilst the rest of society is left to deal with the effects of ever changing climate such as super hurricanes and shrinking coastlines. However, the coastal cities that end up underwater will make nice places for new coral formations, which will in turn help the ocean wildlife population expand, which means more food for humans.
We should also work toward building more durable structures and communities in disaster-prone areas, i.e. buildings better designed to withstand hurricane and tornado winds. Perhaps underground communities would be in order for some areas, so long as flooding is not an issue. Building down is a viable and necessary course as our population grows and cities sprawling across the surface are no longer viable to contain the growing masses. We've already built up with skyscrapers, so we should build down as well. We need to start thinking more vertically and less horizontally.
These 8 Hidden Underground Cities Are Groundbreaking (Literally)
Coober Pedy - Wikipedia
Finally, let's build several generational ships and start sending people out to colonize other worlds. This is a very long term solution but we shouldn't assume our planet will always survive or remain a hospitable place for humans.
And someone mentioned using garbage. We might as well work toward re-using/converting all or most waste, for instance urine and fecal matter might be converted into fresh drinking water and plant fertilizer, respectively. And all that jizz Riker leaves on the holodeck can probably be converted into plant food or something.