Love the topic and replies! My 2 cents - probably no unless infrastructure/ecosystem is built (or lets say available for regular people) for btc payments so anyone easily can pay with btc instead using visa, master etc.
You got a point here, unless the system change, fiat will never be worthless. It requires changes in financial structure to make fiat worthless and not just the price of bitcoin. Even if bitcoin reaches trillion dollar price as long as the finance system does not change, it will never make fiat worthless.
I love to see the price rise that big but I don't think it will make fiat worthless, in fact I think it will also help fiat
to increase its circulation as due to bitcoin transactions will be faster.