It's pretty normal these days to keep at least submix stems if not each individual track as plain audio files, not only for future-proofing but for shifting to

It's pretty normal these days to keep at least submix stems if not each individual track as plain audio files, not only for future-proofing but for shifting to other software to do the mixing or mastering. Admittedly any processing not burnt into the tracks is lost but that was true of analog multitracks too.