How is a to-do app "should/could be OS features?" Or a camera app that uses the volume button? Or Instapaper? I don't think there is an obvious way to tell wha

How is a to-do app "should/could be OS features?" Or a camera app that uses the volume button? Or Instapaper? I don't think there is an obvious way to tell what Apple has in their roadmap. Specially when they publicly downplay the importance of some features only to implement them later. Maybe they should make their roadmap public? :)