Google TV Live Guide can display live channel guide data from apps. Currently, they support Sling TV, YouTube TV, Pluto TV, and possibly more.
Channels should expose its Guide data so that, in the future, it can be integrated into the Live Guide in the Google TV UI.
Sony and other TV manufacturers are moving to Google TV as their primary interface on top of Android TV, so the demand for integration will be beyond just Chromecast users.