It'll be interesting to see if the government has to bring back the $500 bill as the dollar loses purchasing power over the next several years. Or alternatively, they could just eliminate paper currency altogether and force everyone to use an eDollar! Imagine that...
The cent has been irrelevant for decades, and at this point so are nickels and dimes. People talk about it, but nothing gets done about it. Cash itself is being deprecated. At this point, if you use it to pay at the grocery store, the folks behind you in line give the frowns that used to be reserved for people writing checks, and before that were reserved for people that made the cashier drag out the credit-card impression stamper.
Good point, digital currency is already here, many stores that I frequent are credit or debit card only at Costco you have a choice to stand in a bigger line and use cash or a smaller one and use a debit card.