It can never be destroyed you need the blackchain for the mean reason is, you have to understand what blackchain is,in about 10years has been invented blackchain has already done so many things so it can never been easily destroyed it have a big role in bitcoin it's served as public transaction ledger of crypto currency it is invented for bitcoin made it as first digital currency to solve the double spending problem without need of a trusted authority or central server it is also inspired other applications so how can be blockchain system be destroyed if it has played a biggest part of the market right now.
I don't think that the blockchain can be destroyed. This will not happen because this is a very smart system. I have also heard from those who have experience in mining that the blcokchain system is very powerful and smart technology that will provide many people with many opportunities and great things can also be given by this system.