For me, it's more what I'd like them to remove: cost. It would be great if they would expand the Apple TV product line by acknowledging that not everyone wants to be able to play games through their Apple TV. An "Apple TV mini", if you will, would require less built-in storage (cost savings) and could use a non-X series processor (cost savings) as it doesn't need to maintain parity with Apple Arcade. These changes could get us back to the $99 price of the Apple TV 2 (or lower!).What, specifically, is it you want to see them add to it?
I just got a Roku 4K streamer in anticipation of their AirPlay 2 implementation. We'll see how it works in practice once that update is out. Maybe Apple is happy to seed this part of the market to them. I'd prefer the Apple TV UI, but not for a $140 premium.