you are wrong because you are only focusing on one part of bitcoin. it is true that bitcoin is an idea but also bitcoin is a currency, a payment system that is working globally and this system like any other system can die one day and disappear. the idea isn't going anywhere and it will be built on but the system itself can go away.
but that doesn't mean it will though at least not for many years, possibly not in our lifetime.
If the system dies but the idea is alive then people will just build a new system with the same idea perhaps different properties. So bitcoin really cannot die along with BTC.