Re: your Visa comment, these folks are trying to make a Visa card that uses Eth: https://www.mona.co/
And the scalability of Bitcoin and Ethereum type blockchains seems like a plan for failure. The size of the blockchain is silly for the average person to download. Maybe DAG solutions like IOTA or ByteBall are the way of the future for eCommerce. See:
https://IOTA.org
https://Byteball.org
RE: My take on cryptocurrencies current state