They already do. Apple TV app happily shows me Netflix, Amazon Prime, Hulu, etc etc content for me to watch. Their suggestions on things to watch also include content only accessible from those services. My Netflix and Hulu (and HBO and others) are even billed to me via iTunes too, so this isn’t a huge shift in reality. Almost everything but the more polished UI (and not needing to wait on the provider’s app to load, looking at you Hulu with your terribly slow app) is available today in fact.