The only other possibility is the retirement of the $5 banknote for a $5 coin.
I would be fine with that IF the whole coinage system is redesigned to make all of the coins smaller. Nobody wants a dinner plate-sized $5 coin. A coin worth $1 in 2019 should be no larger than a nickel.
As for digital cash replacing bank notes and coins, I'm not a believer. There will always be a need for physical cash: Church thrift sales, garage sales, Girl Guide cookie sales, poppy fund donations, anywhere when the power goes out, when the payment network goes down, the list goes on and on. I always have at least $100 cash on me. I rarely use it, but I still always have it.