I should have mentioned - I don't mind Netflix (and Plex) not being included.

Maybe it's a big jump in my head, but the apps that I want grouped together are the "traditional" (cable station) apps that are usually low quality and require a multi-step 'activation' process to work on every device.

I can deal with a few standouts if it means I don't need to remember what TV station x or y is on.

This is just me guessing, but it kinda feels like Plex won't either.

Unlike Netflix, Plex doesn't have any interest in directly controlling content, so I'd be really surprised if they didn't participate. tvOS/iOS TV app integration would be a great selling point for the Plex Cloud and Plex DVR premium features.

Well it depends if the TV app is available through an open API, or whether you must be invited in by Apple much like their TV Siri and universal search integrations.