7.1 surround sound

Isn't that what a soundbar does? Combine channels in one speaker? 

yes but that wasn't my question

Actually, the Arc is 5 channels, left, right, center, Atmos left and right.  Bond it with surrounds and 2 Subs gives you 5.2.2.  

And who is the "all" you speak for?

But it is an answer.  Arc is a soundbar, which by definition combines channels into one device.  

@futurecrnawebb

What you are asking for is two additional surround channels (speaker). Where do you propose to position those speakers?

One on either side of a room in the middle of the left and right wall. 

Four (includes current surrounds) positioned in an arc pattern across the rear

Should those speakers (4 total) be wall or stand mounted or a combination of both.

My choice would be for Sonos to develop a speaker (similar to the One SL) with an upward firing driver. Maybe call it the Sonos One SL Plus. It would be an upgrade for the Arc and Beam to complete the Dolby Atmos feature (more so for the Arc).

IMO there’s no need to incorporate a voice assistant feature to supplement the Playbar or Playbase.  Additionally, no need to make them capable of being used as a stereo pair. The Sonos One fills that need.

Eliminating the aforementioned features should also help keep the price point at an affordable level. In short the speakers would only be sold as a pair. A one-trick-pony 🎠 LOL
 

I currently have Arc + Sub + Five (LR/RR Surrounds). I recently upgraded my Ones as surrounds to the Fives. It would be nice to be able to utilize the Ones as either Front L/R (to take some of the load off the Arc and use the Arc as Center+Height) or an extra L/R surround (to be placed laterally from viewing/listening position). I have read that bandwidth may be an issue with this kind of setup, but am hopeful that future updates may be able to work this in. 
Using them in any other capacity, as in desktop stereo setup for the MacBook Pro, is still slightly dissatisfying as there is a definite syncing issue when using AirPlay. 
The Ones are powerful speakers and I would hate to see them sit unused. Sony has recently figured out how to use 4 speaker pillars to provide a total surround effect, so I know it’s possible. 

Thank you so much for your reply. It gives me hope. I love sonos. The ease of use and the quality of the products. I have the same set up as you but went straight to the 5's. The ones used as you suggest sounds like a great way to round out the Soundstage. Hope Sonos makes it happen. 

I would also like to request this feature. We own 4 Sonos ones with a beam on the way and going to get a sub in the future, being able to combine everything for a 7.1 setup would be awesome.

Why do you claim to speak for all of us? It won’t make me happy to have 7.1 surround; I’m quite content with 5.1. 

Never say never, but a soundbar is a soundbar.  It’s not a center speaker, and I highly doubt Sonos will (or even can) enable it to be a center speaker.