This is in internal testing. I don’t have exact timing for you, but wanted to let you know it is coming!
We are still considering this feature for future releases, and will continue to update the status when it changes.
We acknowledge the customer demand for Private Channels and have been hard at work on it. Private Channels is currently in preview with a select group of customers. We expect to release the feature to the public later this Fall, and will update here when we are starting to roll out to all customers. We appreciate all the feedback you have provided to us on this forum and thank you for your patience.
This request is still on the backlog.