This is very possible. The Blockchain technology is a revolutionary one with a lot of significance. As the people become more familiar with it, the adoption and utilization of the Blockchain and cryptocurrency will increase which will gradually lead the world to cashless.
it's very possible to cities or communities with high tech living. cashless societies are possible to exist.
Not until a city or a country will have access to decent internet connection or even 24 hour electricity then we cant achieve the goal of having a cashless society. There are still city where electricity is available only for a few hours or on rotation only. There are even cities where the word internet is still an alien word to them.
but across the globe going digital, thats a very very long way to go. as he said above, there are a lot of communities which are deprived of decent net connection, might as well electricity