Many people have gone to wall mounted TVs and use the internal speakers, or wall mounted soundbars. No more TV stands taking up room etc. The current Apple TV can usually be hidden behind the TV, or on a small shelf near it.
The homepod design would work very poorly for this. No to mention the homepod speaker is meant to fill the room with sound, not provide directional surround sound like proper TV speakers/soundbars/home theater setups. They are not meant to be used for Video use.
Now a Apple designed soundbar with Apple TV and Homepod functionality built in could be a very interesting device. It will probably be much more expensive though (I would guess $750 or more). However, you run into the same issue here as you do with building the Apple TV into an actual TV set. In 2-3 years the TV portion of the device will be outdated to the point it will need replaced, while the speakers etc would still work fine. Nobody is going to want to spend another $750+ to replace it every few years. But replacing a separate Apple TV box for $150 is much more feasible.
TVs tend to last at least 5-7 years before they need replaced. Longer if you aren't worried about keeping up with the latest tech. Speakers can last 10 years or more and still be perfectly fine. Streaming devices are outdated every 2 years or so. I'm much happier with replacing my Apple TV every couple of years and continuing to use the same TV, Speakers, AV receiver, etc.