At some point in time, people will use every day satoshis as a unit of currency in order to buy things like vegetables, groceries in general.
And what would happen to fiat currencies? Will they cease to exist? Or will they coexist along side BTC?
Satoshis will become the new money standard in people's daily life.
I'm 120% sure that the governments around the world, bankers, and pretty much the world economy, will never let that happen. If you need someone to explain to you why exactly a centralized cryptocurrency won't ever become a global currency, you need to read a bit more.
The more the whole bitcoin unit keeps expanding its price, the more value a satoshi also will have.
Well, since it's price will keep going up, doesn't it mean that BTC can be a profitable long-term investment? If so, wouldn't this outweigh the need of wanting to spend your precious satoshis?
IMO majority of peple (crypto newcomers, regular folks, the average joe) will only look at BTC as an invesment rather than a medium of exchange (unless something drastic happens like retailers accepting btc as payment, but that's another debate). This isn't exactly what BTC was created for but it is what it is.