I do not really think McAfee's predictions are viable with the current methodology of bitcoin. Yes, it is slow. If you know it is slow that is something you can work around and you can treat it like getting access to your safety deposit box. So if it were simply the slowness at issue then I believe his prediction would be accurate.
However, when bitcoin hit around the $20,000/BTC a much bigger problem reared it's head. At that point the fees to move your currency anywhere were usually $36 to $100. In one case I had $138 worth of bitcoin that could not be moved because the bitpay wallet said I had insufficient funds for the fee. I was trying to withdraw it to a bitpay visa. This means the fee at the time for moving bitcoin was MORE than $138!!!!
I stopped using that card at that time. I also stopped sending bitcoin anywhere. What bitcoin I have at this point is simply on exchanges and I use it to purchase and convert to other currencies.
To me bitcoin is extremely unattractive as a currency. It is for all intents and purposes robbery and unusable as a currency. Why? Those fees.
So if it were to hit $1 million per coin then those fees should be fifty times what the fees were on that day.
That is $1,800 to $5,000 fee just to move your money. That is insane. I think that is the #1 reason that bitcoin will not hit $1 million per coin.
If it were to hit that then the miner fees would need to be drastically reduced. There is a little too much greed involved when the fees are so insane. I do realize those fees are used to prioritize tasks. So what? It is a market. If the fees become so unattractive then the project fails.
It is why I no longer use bitcoin for any purchases. I no longer withdraw bitcoin, I only exchange it. Prior to that day I was using bitcoin for most of my purchases. It was what I'd convert to fiat when needed.
In a way the insane fees did me a service. I found much better ways to achieve my needs that save me a ton of money compared to what I was losing by using bitcoin as a currency.
So if these predictions are to happen bitcoin needs some severe changes to it's fee structure. Otherwise, I don't see any sane market using it as a currency. Also I am on some exchanges where I own no bitcoin. In those places I use ethereum as my exchange medium. If I could use steem as an exchange that would be a no brainer as ethereum is faster than bitcoin, but it is still pretty damn slow. I've done some experiments with speeds of Bitcoin Cash, Ethereum, and Litecoin as well. Out of those litecoin was the fastest. Though all of those are way slower than steem.
I do think bitcoin will still have some high moments. I just don't think it will reach the predictions of McAfee.
EDIT: IF these fees remain then the entire LIGHTNING NETWORK Some people are hoping for would be a moot point. The fees are becoming a far bigger issue than the speed.