This feature request is working its way through the backlog queue. No new details are available yet.
The feature is already partly there. If you have a site collection created with a modern team site at the root, you have a link in the bottom left that allows you to create a Team based on the site. The feature is not available on modern subsites of the root. Perhaps this is in development, perhaps not - as Microsoft is recommending one site per site collection.
This item is still under review. I’ll keep following up with the feature team and sharing all your feedback.
Sorry for the delay on an update on this one! I’m hunting down the status for you and will update once I have it.
Also, if you are interested in participating in testing or surveys for this, just tweet me at @skprufo.