There are many things about a currency that we don't know yet. That are important, but we don't see their importance yet.

talks about using greesham's law to our advantage.

http://www.oftwominds.com/blog.html
Charles Hugh Smith talks about locally created currency, that is created by actual work in the community.
This also goes along with local script being created back just after WWII. It allows for enough money to be local, and that local money is traded faster (greesham's law) and so everywhere it was tried, almost full employment was reached.

Also, locality is important. As in, you help your family first.
So, there will develop world wide cryptos, but there will be like five big ones. One for every continent/group. (and it will have smart contracts, escrow, automatic payments...)

And then there will be tons of local cryptos that come in and out of circulations as the need arises.