100% depends on how much software abstraction the ps4 devkit uses. if the pro is anything to go by, b/c isnt a garentee on the ps5, but its a 100% it will be on ms console.
Leaving aside that a mod with a good track record (Matt) and Kyoufu making a couple of account endangering (if proven wrong) statements about it, Mark Cerny has been granted a patent for a BC mode of operation that, if I understand it's main principles, negates the abstraction layer issue.
I don't want to derail too much about BC, but wayyyy back at the start of this gen on the Old Country I argued that PS4 was basically an ecosystem reset for Playstation - Sony leaving behind the legacy of the first three consoles (which is why despite the ease with which it could be done direct PS1/2 BC hasn't happened despite Sony's history of leading the field with BC) and beginning something new.