You’re speculating long into the future. I don’t know or believe that the future looks the way you envision.

Monero has infinite inflation so saying that it’s identical to bitcoin is wrong. Bitcoin has no inflation. Supply limit is capped. Monero’s supply is not capped. You are comparing Bitcoin’s issuance of a capped supply to literal inflation in monero. It is not the same thing.

If monero’s market cap remains low and the price doesn’t improve, it will not work as a medium of exchange. Selling a couple million dollars of monero would tank the monero price. Your medium of exchange “may” still be private but you’re poor now. 

 Selling for products and services won't tank the price. That's what a circular economy is for.

Monero's disinflation is limited by time and known 1000+ years in advance.

It's a tradeoff made to guarantee security of the network in case fees are not sufficient.