Sure, but you could even e.g. dynamically change the number of lanes and their direction, which would be much harder to do smoothly with physical signs and lane

Sure, but you could even e.g. dynamically change the number of lanes and their direction, which would be much harder to do smoothly with physical signs and lane markings. Roads could become wide unmarked surfaces of pavement where everything is dynamic. When smartphones went from having small screens and physical buttons to iPhone-style blank slates for any content, they got a lot more powerful and people came up with lots of innovative uses for them. You could imagine the same thing happening with my example of roads when it becomes essentially free to test new ideas for how traffic should flow, etc. But again, this is all just a thought experiment. I don't expect it to actually happen.