The potential price is not limitless there is a limit to how much fiat there is on the world and if at some point bitcoin becomes the main currency of the world then the price against fiat is going to become irrelevant since bitcoin will become the new point of reference, so instead of thinking of the price of stuff in dollars you are going to think of it on terms of bitcoin.
with respect i don't ever think bitcoin take place of fiat currency , because of violating and sharp movements , people need something more stable , Bitcoin would be more popular but i think it would be used as a sub currency , as a second place after fiat currency.