You use an intermediary that will vouch for you in the meantime — say like a credit card company.

Seriously, if it reaches that point, sure maybe Bitcoin is not going to work and we will pick something “new,” but for payment processing it doesn’t matter as intermediaries will pop up as they did for cash.

Edit: Disclaimer: I worked and work on that “new” stuff.

But is that really Bitcoin at that point?

Bitcoin Lightning is used for such transactions.

I heard Cashapp's lightning implementation works well.