I'm not so sure I agree with your last comment. If it had a camera it could finally mean FaceTime on AppleTV. That would be a useful thing. We occasionally mirror a phone to the TV for this purpose but it's awkward at best.
Why don't you get a FaceTime call going on the phone and prop it up on the front bottom of the TV (tossing the other end of the call to the TV). Now you will seem to be looking right at the other person and they at you... much like putting a camera in the bezel (albeit bottom bezel in this concept) like a giant, upside down iMac or Studio screen.
As mentioned elsewhere, my preferences would be for NOT merging such things together. If Apple wants us to FaceTime on TV, give us something like the original iSight camera to mount on the top bezel of
any TV, perhaps powered by USB in the TV, else run a USB connection over to a (resurrected) USB jack on an AppleTV puck. Ta-dah: perfect Facetiming on TV while being able to position AppleTV anywhere (including completely hiding the puck BEHIND the TV as many do).
Else, one has to assume central placement- as close to the TV screen center as possible- which then demands a soundbar/AppleTV/camera all-in-one. First, not everyone leans on a soundbar. Second, AppleTV guts will be the weak link in such a thing, likely to be obsolete long before the speaker or camera.
For me anyway, I'd much favor keeping such things SEPARATE:
- iSight-like camera peeking over the top of ANY TV (much like front-facing in existing Apple devices)
- AppleTVs as separate "brains" able to be placed anywhere anyone wants to place it (and replaced when it is obsolete)
- Speakers not mostly limited to only soundbar setups.
- "home pod" smarts as a separate EchoDot like box that can be replaced when it is obsolete.
Camera and Speakers will likely be great for 10-20 years. AppleTV is probably good for about 5 or so. HomePod smarts are likely good(?) for only 5 or so too.
Or to simplify that, blend HomePod smarts not already replicable in AppleTV (are there any?) in tvOS update and it covers the "smarts". Since both of those likely obsolete when the core iOS that underpins them obsoletes, both of those naturally get replaced anyway at about the same time... unlike the speaker and camera which could be great for YEARS.