As of early next year, the Fed (US) will not accept anything other than ISO20022 messages on their networks. So any banks that are using Fed networks are required to use ISO20022.
I work for a large financial institution and we've been migrating our Fed network processing to ISO20022. All financial institutions we work with, and vendors who process payments for fraud and such, are also doing so. I'm highly skeptical of the date, but it is going to happen.