It's sad that even if developers wanted to develop for O or P, they can't because you can't even buy units running those versions. Unless the devs happen to work in areas that use the STBs and sigb up their employer for a cable tv subscrption I guess.
They had to release a developer unit as a last resort just to get the latest OS's into peoples hands.
The other point to make here is along with Android Oreo comes Google's Project Treble
Going forward this will have significant benefits for hardware sellers because once they have an Oreo compatible vendor interface implemented in device Firmware, any new updated Android Operating system can then be much more easily implemented.
Users will also likely see much faster Android OS updates across all Android platforms. Cheaper for all ATV device sellers as well.
Jared is one of my favorite writers. He writes about Android TV often, and I like his perspective here. He makes great points about Google needing to get the entry price point down for a quality Android TV experience and push out a wider variety of devices. He also talks about Google's role in attracting app makers to create & update high quality apps.
I think Google has been clear about a three legged strategy of Android TV powering TV-operator boxes, embedded TVs, and Set Top Boxes/Hybrid devices. The first two appear to be going OK, but they need more Set Top Box or Hybrid devices on sale & in use for market share.
Assistant would seem to me to be the key. It's the primary focus for Google, and as the JBL preview shows it can be a complete experience w Android TV that it can't with a Chromecast or a non-Google platform. I think of that as a Max version of what I want. A mid-priced ($80-120) device that's a Google Home for a living room with Android TV + Casting built in. Won't sound as good as the JBL, but would cost much less.