There's no such thing as forever but Cryptocurrency can evolve just like the car and phone technology, but as long as we are living in advanced technology and there is no war it will not die, and on war, this is something that even the most powerful nation does not want to happen because even if they win they will still come out a loser.
Because war is not fought in terrain anymore it is now fought with technology, it can wipe out territory with just one push of a button.