I’d just point out that these microorganisms will definitely escape into the wild at some point and then durabilty for plastics will be similar (maybe?) to that for wood (there was also a period in time when trees evolved when microorganisms had to catch up to degrade it, presumably it was full of wood everywhere that just wasn’t rotting).
Imagine a future where your PC screen or mobile phone has an expiry date and it’s not due to planned obsolescence. Maybe that’s not so bad after all, now that I think about it.