That's our mistake - it's still 4096. Assuming you saw this on the Playground, we'll fix it shortly. If you saw it somewhere else, please let me know.
https://platform.openai.com/playground/chat?model=gpt-4-turb...
https://platform.openai.com/playground/chat?model=gpt-4-turb...
Edit (4:57 ET): "gpt-4-turbo" shows the updated 4096 in playground. "gpt-4-turbo-2024-04-09" remains 2048 in playground.