That's the thing: with proper dedicated peripherals you don't need the software-defined coprocessors.

Sure, they are great if you want to implement some obscure-yet-simple protocol, but in practice everyone is using the same handful of protocols everywhere.

Considering its limitations, betting on the PIO for crucial functionality is a huge risk for a company. If Raspberry Pi doesn't provide a well-tested library implementing the protocol I want (and I don't think they do this yet), I wouldn't want to bet on it.

I think they are an absolutely amazing concept in theory, but in practice it is mostly a disappointment for anything other than high-speed data output.