The APIs I mentioned in my previous comment don't exist yet. My point is that Google is going to need to _build_ APIs to fulfill all of the most common use case

The APIs I mentioned in my previous comment don't exist yet. My point is that Google is going to need to _build_ APIs to fulfill all of the most common use cases (including those ones) in order to succeed in their goal of making extension permissions more fine-grained. So yes, the functionality of most popular extensions will be covered by the new APIs, because Google will designing the new APIs with those popular extensions in mind.