One thing that would be optimized with future and technology would be to have more apartments to our taste, while there's less space in the apartments. Better space management could be done and thought about in the future.
An example is the convertible sofa we have today. If we push the concept further, we can get something else even better: full rooms convertible one into another. While this would limit how much people could live in that place because they couldn't do many things at the same time. Another way to go would be to put one room upside down and a room on the normal ground, so the space "wasted" by roof could be used, to the extent everything is done to be comfortable even upside down. Perhaps gravity change.