On the contrary, if it ever shrank to an extent that posed an existential threat I think it is almost certain that a different consensus algorithm (such as proo

On the contrary, if it ever shrank to an extent that posed an existential threat I think it is almost certain that a different consensus algorithm (such as proof of stake) would be adopted. There's no telling how the legalities surrounding crypto currency will evolve but I seriously doubt that it will ever disappear.