GPT-5.2 and GPT-5.3-Codex have been sunset in Codex with ChatGPT subscriptions

No. Codex 5.3 is not available through copilot which anyways would require a costly Github upgrade - Copilot is useless unless its upgraded to use Claude Sonnet 4.6 which could according to some experts be as efficient as codex 5.3 (but no price wise)