There's some talk in this thread that portrays a future system that's any different than what it is today.

It doesn't have to be. And it probably won't be.

Waiting for confirmations to propagate is impractical for the same reason today's vending machines won't accept checks: Confirmation takes too long.

That's the whole reason why we have electronic spending with credit and debit cards. It's what enabled our fractional reserve system in a global economy. Your assets are just a number in a database that only represents Dollars, Bitcoins, and Zloty.

The instant transaction layer on top of Dollars and Bitcoins means that the actual transaction of real currency can take an arbitrary amount of time (if it even happens at all!).