Arguably the plastics break down until they become basic short polymers that exist in everything though no? At some point they progress from micro-plastics to non-harmful substances. So having a break point where we stop producing plastics would mean that we stop adding then to the environment whilst allowing the eventual half-life of the material to take its course (granted that's probably 10s of thousands of years from now, but with clean up operations that could be accelerated).
Well, no. Some common plastics like polycarbonate aren't biodegradable, and will basically never break down without application of significant heat/water/enzymatic activity/etc. For some of these, the half-life could be a great deal more even than 10s of millenia: