Maybe another century or probably when the humans become extinct, I don't think that we're going to lose our dependence on fiat, Romans and other ancient civilization used a form of fiat currency and they all collapsed as a civilization and here we are still using the same thing.
Another century maybe, but still no assurance that it will happen. Fiat will continue being used and it won't replace by any innovative
financial system, so far it's still far from happening as we all see that crypto still needs fiat when converting it and use it for your daily transactions.
You can't use crypto in most cases when dealing with your local market. A simple logic that fiat still in need when you have to transact offline.
Maybe if adoption take place and there are more established business to join crypto, it will co-exist but not eliminate the use of fiat completely.