The chance is very low to happen a significant inflation unless world war III or worldwide epidemic disease occur. Let's assume any of this happened. Will people likely to switch their fiat currency into bitcoin?
If that's what happened and people attempt to switch their fiat into bitcoin, there will be a chance of fiat currency become nothing of value.
PS- I don't want world war or epidemic disease at all. i am just thinking at what point bitcoin will take over the fiat currency system.
It will take a very long time before bitcoin will take over fiat currencies, since we have been using fiat ever since. Even if there would be a large inflation worldwide, we cannot expect that people will immediately switch to bitcoin that will be used for canned transactions.
We will come to that time where we will use for our everyday lives, but it is not today.