There are several candidate processes for restoring plastics into virgin materials. If we had an overabundance of very cheap renewable energy (like the excesses during daily peak solar production which are just characteristic of lots of solar) you can just tear the carbon into pieces by getting it extremely hot under high pressure to essentially create new crude oil and start from scratch. In the current world there are some promising enzymes that can tear apart polymers to return plastic to an earlier stage in production which makes it more or less fully recyclable without degradation, but these things are still under development.