> This. There will continue to be improvements to AOSP, but only as that makes driving Google's proprietary apps easier and faster.

This isn't remotely true, work continues on the platform in a number of areas beyond just feature requests from other teams. Having application teams able to explain the pain points they feel in the platform and then having the platform team come up with solutions that work for the general use case is a good thing though, it improves everybody's experience. It isn't like there are hidden "makeGmailFaster" APIs that other people can't use.