How about a HomePod + Apple TV with WiFi extender capabilities built in as well?
Why want all that in one thing? Else, why not Home Pod + AppleTV + Wifi Extender + iPhone + iPad + MBpro + Mac Desktop? All in one concepts can seem great up front but then one part ages too much or is obsoleted by software and you may have to throw it all out. I'm experiencing this right now with an AIO iMac: Apple obsoleted it with macOS updates and now some bit of the tech is blinking out... yet there's still a perfectly good FaceTime camera, screen, speakers, storage, etc in there. One part goes and it almost junks all of the rest.
Speakers can easily last 10+ years without losing anything. So HomePod-type stuff probably has the longest useful longevity of anything Apple makes (assuming the software parts are updated for the life the speaker). For most, HomePod should sound as good in 8-12 years as it does today.
AppleTVs are good for about half that time, until some new standard takes over or we jump aboard the next (8K) train. I know, I know: "nobody can see...", "the chart, the chart", etc- all the things we sling before Apple rolls out a new AppleTV with the next resolution jump to put down that hop... and then promptly drop such statements as soon as they do. I've seen that bash-then-gush/praise show at every hop: 720p to 1080p to 4K.
WiFi extenders might be good for 3-5 years until that standard is significantly updated. And of course, extender usually needs another hardware part to extend from, so that would mean Apple has to get back into the Airport (hardware) business. Great if they do but do they want to do that? Generally, you can't just pair any extender with any other router. So that seems all or nothing vs. just one part intended to work with the wide variety of other mesh routers.
The general perception among even the Apple faithful is AppleTV is too expensive. Add additional stuff to it and it will be MORE expensive.
Not everyone with AppleTV wants/needs some kind of soundbar/home pod speaker. For example, my AppleTVs are already linked to either discrete surround sound speakers hooked to a receiver or existing soundbars I would NOT want to toss to add one with a FaceTime camera.
Not everyone with HomePods wants one dead center of their TV (to get the camera in the right place for FaceTime). As is, it is generally good to spread HomePods out for left & right stereo. Yes, if Apple rolled out a HomePod "center" or soundbar, that would naturally go in the right zone but how many people really want FaceTime and AppleTV jammed into that same box? See useful timetables towards the top of this thread.
Not everyone with FaceTime usages want to do that on their TV... or want to pay up to be able to also do it on their TV. Instead they can use the fine quality FaceTime camera in their iDevice or Mac without having to spend an additional dollar. That also lets them position the camera right where they want it and FaceTime from anywhere. If this is the primary draw of this concept, accomplish this in the FaceTime software so that one can prop their iDevice up in front of their TV screen and airplay the person on the other end to that TV screen. Conceptual cost of that option: free.
Would some people be interested in this device? Of course. I'm confident Apple could box air and people would be tripping all over themselves to buy empty boxes... and then potentially smothering because they refuse to breathe anything but. But beyond the fans who will line up to buy ANYTHING, the market would likely have to be those wanting to pay up for what seems like the most expensive streamer in what is probably a premium priced soundbar attracted to the idea of using proprietary FaceTime through the thoroughly fixed location of their TV.