Cryptocurrencies seem to be a valid alternative to fiat currencies printed by nations however has the debate about whether gold/silver are still king been concluded? Bitcoin/Steem etc seem only valid when everyone plays nice. However exchanges and computers can be hacked or manipulated. And as result the digital value can be forced to zero fast. It's much harder with tangible metals.
This is a good question! How it is the World now (and the way we are heading) I would trust more in Gold or Silver, something more tangible than the Bitcoin/Steem that not only need electricity also internet.
Bitcoin will be very big. It's being featured in all TV shows including "MR. Robot"