Remember 1997, when Yahoo was THE internet search engine/portal/cool place to go on the internet and Google didn't even exist? The Yahoo hype was ridiculous.
Someday, there may be a practical and widely accepted digital currency.
But there's a good chance it won't be Bitcoin or Ethereum or any of the other "me too" currencies that currently exist.
My bet is that in 20 years, Bitcoin will be in about the same position as Yahoo today (basically, in the toilet), and that some other digital currency that probably doesn't even exist yet, will be the leader (the Google of digital currency).