Starting today, paying API customers can access GPT-4, the most capable model offered by OpenAI. The Chat Completions API has become the preferred choice for developers, accounting for 97% of API usage. OpenAI plans to focus on optimizing and improving the chat-based models, as they have proven to be powerful and flexible in providing conversational experiences. In order to prioritize these newer models, older models in the Completions API will be deprecated in six months. OpenAI will provide new models and offer support to users who need to upgrade. Similarly, users of older embeddings models and the Edits API will also need to migrate to newer models.
https://openai.com/blog/gpt-4-api-general-availability