In a way, we won't know what it is until it's done. We depend on the Android OS for some things. But maybe this might help clarify things.
Panel is a user interface only. It's a webapp that MC serves. It can only control MC, either remotely or locally.
JRiver for Android is a native Android App, and it's potentially much more powerful, because it is a port of MC. The MC user interface couldn't work on a phone, so we have a simplified interface that resembles Panel.
Both stress ease of use and speed over power.
In order for any Android App to be approved for Android TV, it has to be able to support navigation from a D Pad (Up, Down, Left, Right, and Enter) so it can be used with a hardware remote. This much is working now, but we're having trouble getting it approved.
It has to conform to the Android TV navigation. I'm not sure if we could do Theater View on it, but there will be a lot of similarities.
We don't yet have video running, but the capabilities will depend on what Android OS supports.