by this logic "something fix" equals to how much the other. will it be like a measurement, 1meter equal to 100cm.
ps: i just remember that i read this in atomic swap topic. someone pointed out this kind of argument. cant remember exactly what he says.
i like to re read the topic if anyone remember it.
Nope. If BTC becomes the only currency in a world with no fiat, it will still be subject to fluctuations.
To give you an example, you have 1BTC that is worth 10 ETH in that scenario, and NASA decides to build a giant colony ship that will go to Mars and the official currency of that ship and the newly formed colony will be ETH. You can expect the value of ETH to go up and ultimately be worth more, for instance 0.15 BTC per coin.
As long as the economy changes prices of goods and currencies will never be fixed. We are evolving, 20 years from now somebody may find a way to crack sha256. If that happens the value of BTC will go down, regardless of whether there will be fiat or not.