I highly doubt that will happen, even the world is trying to create so many currencies. One payment medium for all is not really possible but in the case that is happening the price will go up dramatically, there will be a lot sidechains to improve scaling, and lastly everybody will have better freedom to transact. Again, probability is too low for that to happen, the government didn't issue fiat because they want to out of nothing, but because they realized they could control their country economy that way.
Fiat currencies are not increasing, or very little rise because existences of fiat currencies are strongly correlated with total nations and unions in the world. Such entities don't increase or decrease too much over time, but there has been emerge of Central Bank Digital Currencies (CBDCs) and it's a current trend from central banks globally.
In cryptocurrency industry, altcoins are very inflated and abundant with so many new altcoins, tokens created in three latest years.
https://coinmarketcap.com/charts/number-of-cryptocurrencies-tracked/Click on Total tracked, and All to see that from about 5M in late 2024 to more than 50M now, that's crazy but means many altcoins, tokens are useless.