Theres a reason why Bitcoin was called a bubble..
I strongly believe Cryptocurrency will bounce back... but in a different form with a higher hash function than SHA-256 and probably strictly managed by some elements within the G8.
Bitcoin was a test but the world must still go fully digital in basic finance administration and other areas as well
Tulips were called a bubble as well and they never bounced back. Not all things that experience a bubble will one day recover. Even in the dotcom bubble only a handful survived.
Advancements with hashing functions are probably inevitable if bitcoin is to survive and scale but I don't think it will ever be controlled by the g8 or anyone else, people use bitcoin because of its decentralized nature. Without that it's nothing.
You can buy more than half of all bitcoins or other cryptocurrencies and then they will not be decentralized.Now there is news about 50 % attack on the network, though not yet bitcoin.If the state (government) wants,it will be able to attack many cryptocurrencies in this way.