I guess it depends on the people/community. For example there are countries that literally hate cash due to fake money being a huge problem and prefer digital payments to the point that a lot of the merchants refuse trading in cash. As for cash disappearing completely It's possible the thing is money/cash has existed for thousands of years and it won't be easy to convince an entire population to change. Moreover, for there to be an alternative "online" payment wouldn't it require internet or a network of its own? So I guess on the large scale of things it's possible but hard to predict of certain. Do I see a country eliminating cash in the next 10-30 years? Absolutely!