Does Airplay 2 Support mean this would work ?

Not on Sonos speakers, at least. They still don’t have the capability to process Atmos. Or, if they will, I haven’t seen that part of the announcement.

Guess I am not sure how ATMOS works. If the TV Supports it - and then the Apple 4K TV supports it - does that mean that the speakers need to support it ?

That is really my question - Not sure what it means for the Apple TV piece to have ATMOS AND AirPlay Support

Does that mean that the 4K understands how to decipher and stream ? Otherwise is the 4K just a passthru device ?

Fundamentally - I understand why the Playbase would need the support if it is directly connected to the TV. But if the Playbase/Playbar is now connected as just a speaker - which device is responsible to do what

If the speaker can’t decode the signal, then you won’t hear anything. So, yes, the Playbar in this instance needs to be able to support it. As with the DTS discussion, I don’t see Sonos supporting in the near to medium future. But, in any case, they wouldn’t pre-warn us, unless they release it via the Beta program.

The PLAYBASE/PLAYBAR takes a signal and processes it in order to send out data to the speakers. There are already many TVs that can deal with things such as DTS, etc, and can pass that signal to the Sonos devices, but the Sonos devices don’t have the capability to interpret it. So, sending an AirPlay 2 signal to any Sonos device wouldn’t be interpreted, and you’d get no sound.

The thing you need to remember is that in each Sonos speaker is basically a computer that interprets the data and tells it what to play. If that computer isn’t able to handle anything beyond Dolby Digital, it won’t matter what you send it.

Now, could they update the firmware on that computer to handle things other than Dolby a Digital? I don’t know. There are likely limitations on processing speed, RAM, backwards compatibility, and legal issues with appropriate licensing that I just don’t have any knowledge of. Could it happen? I have absolutely no idea.

It's way too early to say much about it, but Airplay 2 support is coming per this new post:
https://en.community.sonos.com/announcements-228985/exciting-partnerships-in-the-queue-6791309/index1.html

For this specific case though, it isn't relevant. The Playbase has to support it for that to matter.

Yeah, thinking out loud - and I haven't touched any of these devices. But if you configure the Apple TV to tell it what speakers to use - then I am not so sure if the playbase would still be talking to the Play 1's ..

Or if that responsibility is now part of the Apple TV device ..

I would think that the Airplay 2 support is going to force their hand sooner rather than later then

It doesn't matter if Airplay 2 supports it. Dolby ATMOS is 3D sound standart. So since Sonos doesn't support 3D speaker placement, like 5.4.1 surround, you won't have any sound benefits from the Dolby ATMOS support.The best surround sound experience that Sonos supports is 5.1 surround.

However in the future Sonos may announce support for 3D standarts like Dolby ATMOS or Auro 3D, but this will require more speakers than just a Playbase/Playbar, Sub and to Play 1/3/5.

But it may be possible to send a Dolby ATMOS supported signal over the Apple TV to the Sonos system, but you won't here the 3D sound effect (Dolby ATMOS) it will sound just as if it was a normal 2D sound file.