[lxgr]

Sorry to be so direct, but you don’t seem to have any idea what you are talking about in this context.

Banks and payment card processing (which is what TFA is about) are basically two different worlds. One switching to a new data interchange format has essentially no consequences to the other.

While I could imagine Visa and Mastercard offering an ISO 20022 interface for new integrations, I’m willing to bet on the majority of volume staying on ISO 8583 for this decade and probably well into the next. They most certainly won’t force anyone to migrate either.

[cess11]

You don't have to imagine, just go read what the payment processing services publish and promote.

ISO 8583 is a massive liability, just an insane amount of technical debt and nasty workarounds that harms interoperability, i.e. profits. This is why both banks and the payment sector communicate so aggressively on this issue.