Not sure if I'm interpreting John McAfee right, but he said "distributed" exchanges. Does he mean "decentralized" exchanges such as Bitshares? If so we already have those. The problem is that KYC barrier of centralized exchanges allows monitoring of the onramps and offramps (as Andreas Antonopoulos puts it).
So John says that "distributed" exchanges are going to make the difference. I understand that if no one is in charge, then it can't be squashed by the state. However at this point, the existing decentralized exchanges are lacking liquidity (and also partly centralized such as OpenLedger which could be shut down). I'd like to know more about how that will render the banking system powerless in detail.
Right now we have many dependents in the USA (about 47%) receiving some sort of government handouts be it military pension, social security, welfare, disability, etc... Institutional money will not be allowed to play in that space due to the regulations (ETF's for example) and many transactions are only allowed to happen in USD. What this means is that the 3rd world is the main hope here. Those roughly 6 billion people either completely excluded or given only minimal access will be the ones to adopt this and make bitcoin "happen".
Please correct me if I'm wrong, but I don't see this quite happening by 2021. I am however on record stating that I believe that the next moon shot for bitcoin will happen starting by summer 2020.