Not disagreeing with you as this doesn't sound bad but there is actually some theories or ideas I've heard that would mean that cash will never be completely disposed of. The theory states that any stable economy will naturally have a black market trade, and the black market needs cash to survive. I don't really know any details but the premise is that without cash your blackmarket collapses and without your blackmarket your economy suffers. Supposidly the illicit cashflow through the blackmarket is important in a stable economy. I haven't actually studied any of this though so anyone feel free to correct me on it if you know better.