Seems to me that the iDevice on the Belkin hook shown in the show today-
Continuity Camera- could work as well hooked to a TV and wirelessly linking to AppleTV. When I saw that demo, I actually thought of that application FIRST because I've seen so many people seem to want that ability.
Putting a camera in AppleTV (box) is no good because that would demand that AppleTV is positioned in a very specific way very near center of the TV. Some people could do that and others could not.
The integrated soundbar/appleTV/FaceTime camera/router/popcorn maker/shave and a haircut machine/et all concept that keeps flying around assumes that many people want and/or use soundbars... and that when the AppleTV guts in the Soundbar reach end of useful life, apparently the owner will throw the whole thing out to upgrade. Seems pretty niche to me.
The best option that seems like it works without possibly any hardware changes to AppleTV is what was demoed today... just hook the clip to the TV (instead of a monitor as demoed), insert iDevice (or perhaps only iPhones work?) and wirelessly FaceTime via that screen. If I wanted this feature, I'd just get a clip for the TV and another for the computer monitor and put the iDevice on whichever I wanted to use for that functionality at the time. Looks towards perfect in terms of working with pretty much any setup scenario, any speaker setup scenario, whether AppleTV is front & center or velcro'd behind the TV or off to the side in a cabinet, etc.
I'm actually surprised that THIS feature was not announced for AppleTV today but hope that it is in tvOS 16 (or 17 or 18).