> So a single BTC will be worth millions in 50 years, got it.
If bitcoin (or any other supply-limited coin) remains popular for such an extended period of time: yes, yes it will. And not necessarily millions in relation to other currencies. Even within itself. It's limited.
Example: "The Solana Foundation has announced that a total of 489 million SOL tokens will be released in circulation. At the moment, about 260 million of these have already entered the market."
There are 9 billion people in the world. By the very definition of a limited coin whoever got hold of the initial supply will be richer (in Solana) than anyone who didn't get there in time. Forget 50 years from now. Already now there aren't enough coins in circulation.