The banks will be fine. Australia implemented a similar system a while back (NPP/Osko) which is a standard adopted by 100+ banks. It was designed as a replacement for standard bank transfers which usually took a couple of days.
Now, even transfers in the tens of thousands move instantly. This was also a response to apps like Venmo potentially entering the market - now you can just pay to a phone number or email, as long as it’s been explicitly linked to a bank account. This is by far the preferred way to send money here and third party apps are not common.
They’ve also now introduced PayTo which manages debits and payments online with no fee. You simply approve the transaction in your bank’s app.
Australia also has widespread Visa and Mastercard use, but Eftpos has always existed - which is a fee free alternative around since the 1980s. It supports contactless, but that isn’t widespread due to weak international support and can only be used with debit cards.
The downside is that new features need to be implemented by each bank app, but it’s been interesting to see some of the smaller credit unions collaborating for example.