Fiat is to a large degree already digital, much of the fiat are just numbers in a computer, which are in only a few servers controlled by only a handful of people.
Currencies have been under heavy inflation in the past, for e.x. there are banknotes of 250 000 000 Zimbabwean dollars.
The more the money is printing, the more close to that situation we will get. Consider this theoretical  example:

Average cost of bread

year   cost ($)
1930    0.09
1940    0.10
1950    0.12
1960    0.22
1970    0.25
1980    0.50
1990    0.70
2010    2.00
2020    4.00
2030    8.00
2040    16.00
2050    32.00
2060    64.00
2070    128.00

At this point, will people  still use fiat?