Gold will cease to be meaningfully scarce if we ever mine an asteroid or something like this, but the barriers to that are obviously somewhat higher.
Since Bitcoin is divisible down to a small fraction, and you can trade it for whatever price you'd like, it makes more sense to me for the two parties involved in a Bitcoin transaction to take some tiny fraction of a coin and use that as a token to transfer the value from one party to another. You'd convert fiat -> BTC fraction -> fiat almost immediately.
You would have the benefit of the decentralized network to make completing the transaction much easier, and by using a fraction of a coin you'd remove risk caused by exposure to fluctuations in the value of a whole BTC.
The most prominent "fork" of bitcoin (bitcoin cash) is still only about 45 days away from having their entire history since the fork rewritten using just 25% of the available hashpower.
In a little over a month, they could re-mine every single block since the fork changing which transactions are included. And that's the most popular fork, rewriting the entire chain since the fork. If you want to rewrite just the last 50 or so blocks? You'd need something like a few days and a few percent of the overall hash power to do it.
Are you in possession of like 1% of hashpower? Then it's more than possible for you to send something like 100 BCH to an exchange, wait for the 10 confirmations, then go to work rewriting the chain from that point to "current" without your transaction.