I’m sure we’ll learn more about tvOS at the September event specially if they’re planning on launching a new HomePod that will run tvOS and may have features that interact with TVs or replace the Apple TV box itself.
The focus has shifted to the TV app for video content, away from apps on the Home Screen. tvOS apps that aren’t streaming video haven’t taken off in all these years. Apple has to rethink Apple TV and I believe they already are.
SharePlay is taking a leading role in how content from apps on one device are shown on other devices. Having Arcade run on an iPhone, iPad or Mac and displayed on a TV is a better way to do apps on a TV.
So instead of having an app on the Apple TV box, they’d live in another device and be streamed via AirPlay to TVs that have it built in or via a simplified AirPlay stick, that just contains the TV app and AirPlay capabilities.
Apple usually introduces technology that is a hint for upcoming changes in other devices. The iPhone camera in macOS and the clip is a great fit for a TV. Start FaceTime on your iPhone, AirPlay to your TV, then clip it over your TV. No need for a FaceTime app for tvOS. I can think of many other examples like this.
This is probably why tvOS wasn’t featured since a major reimagining is in the wings, best introduced at the consumer event in September.