As for me, fiat isn't losing its value despite the increase of people who are using digital currency. Cryptocurrency still has to go through before it surpasses fiat. In our country, people who are using our local wallet still convert their crypto into fiat to spend it with their necessities so I guess we're still far from replacing fiat. Both bitcoin and gold still rely on fiat at some point.
Bitcoin and gold are both and investment in which grows year by year. But as for fiat is still be there, we exchange gold and bitcoin into cash, we are not yet using bitcoin directly to purchase ang thing that we want but also there are some stores who accepts it but they are few. Maybe in fiat it decreases its value but it is not losing it worth.