That’s already how it functionally worked for each major release

Here’s their previous strategy: web.archive.org/web/20220917195332/…/codelines

Google works internally on the next version of the Android platform and framework according to the product’s needs and goals

When the n+1th version is ready, it’s published to the public source tree

The source management strategy above includes a codeline that Google keeps private to focus attention on the current public version of Android.

We recognize that many contributors disagree with this approach and we respect their points of view. However, this is the approach we feel is best and the one we’ve chosen to implement for Android.

As far as I can tell, this would really only affect QPRs, since the public experimental branches that get made after they throw the next release over the wall is going away