Bitcoin/Ether barely register in terms of the total economic activity (75 Billion $). With significant fraction unusable. They will either be tamed or destroyed.
In fact another way of looking at cryptocurrencies is as a revolt against the Visa/MasterCard duo-poly & regulations that has made digital transactions too difficult. The moment digital transactions become cheaper/more-efficient, the allure of crypto-currencies will disappear.
As for the allure of cryptocurrency, only time will tell. I predict they will continue to grow in prominence.
Except for drugs, contraband, money laundering, and evading capital controls. Which, from day one, has been the entire actual value of these things and remains so.
That's a reasonably big business to be sure, but it will always remain a niche element and always be under fire, for obvious reasons.