The only way to destroy bitcoin is to shut down the internet. There will be no way to transfer bitcoin from person to person since the internet is the essential tool to perform bitcoin activities. Unless they would develop offline bitcoin or else the widely used payment method is through fiat money.
You're wrong, bitcoin can be destroyed by another cryptocurrency. Yes, you read it right because if there is another cryptocurrency that will be popular and better than bitcoin then that will become the reason for bitcoin to be destroyed and there is already a lot of altcoins in the market that can compete with bitcoin but i believe that bitcoin is still stronger than them so the destruction of bitcoin will not come fast and it will take a few more years.
It would take quite a lot for that to happen.