Why are you waiting for the API? The OpenAI Playground has API examples you can copy paste. You can go over 4000 tokens if you have a business justification and payment method. You have access to most of their models even the new Codex ones
Edit: Looked at your link and I misunderstood. I think I understand you're waiting for the ChatGPT specific model now?
You are correct that I was incorrect. Thank you for correcting me. I misread their documentation. Sounds like they might increase the token limit in the future, but right now it's 4097 tokens shared with the prompt
Edit: Looked at your link and I misunderstood. I think I understand you're waiting for the ChatGPT specific model now?