The US seems to have entered a stasis of coinage (and bill) denomination since before I was born (a long time ago). Besides getting rid of the penny, pretty much every attempt to introduce new currency (like $1 coins) have failed. And I wouldn't count on being able to use anything bigger than a $20 bill at a random ___location.

And, at this point, cash use is in sufficient decline that I can't imagine any serious effort to make changes.