I do not have a publicly available release date for the leaving beta status. Subscribing to the Developer Changelog is your best bet for being the first to know about this release.
In regards to your other question, I have to share the official answer of:
Please note: This API is currently under development and is subject to change based on testing and feedback. By using these endpoints you agree to adhere to our Developer Terms& Developer BetaTerms. You also acknowledge and understand the risk associated with testing an unstable API.
I hope that is helpful. Please let me know if you have other questions.