So here's for a very unpopular opinion: I sincerely hope that a lot of "AirPlay 1" speakers will not support "AirPlay 2". Let me explain why and also why I think Apple is going for this approach.
Multi-room audio is very hard to do because of network latency. One commenter also mentioned things like EQ and delay between digital to analgue conversion. While true, the biggest challenge with multi-room audio is network. If you have a slow home network, the chances of off-sync audio between rooms increase significantly. To solve such a problem, the speakers need to work out together (read: computational power) which is the weakest link in the set-up and ultimately all play with that same delay. I'm pretty sure Sonos does this as well.
I believe that they have already said that the AppleTV 4 will be part of Airplay 2. The AppleTV is typically hooked up via HDMI to a TV, speaker or receiver via HDMI. Apple still can't control the DACs/processors in all of those different devices, so even if all of your AppleTVs are in sync, they could still have issues on how long each device they are hooked up to handle the digital signal.
They could use the iPhone as a way you could walk around and have its mic listen for the audio stream and then they could automatically adjust the devices latency individually assuming they were streaming from the cloud rather than using the iPhone as the music hub like they do now.
I still think there is a possibility that many of the Airplay devices could be updated. However, companies like Bose (just one example) may prefer selling you another product rather than giving you an Airplay 2 update, so a lot is still unknown at this point.
[doublepost=1496759879][/doublepost]
I don't get the point of multi-room audio. I didn't get it back when all AV receivers suddenly went multi-room, either. Why would I want my music to play in a room that I'm not in? Shouldn't the people in that room choose what's played there? Selecting the destination speaker from the source device works fine for me. Besides, playing the same music via multiple speakers simultaneously already works with Airplay-1.
I could see a (very) slight point in it if the music would follow me as I move around the house, but that seems gimmicky and I doubt I'd be using it much.
I agree with you to some extent, but some people like the same music playing all over the house. I have used that feature with Airplay when we have parties.
Outside of that, it is detrimental to sound quality because having music bleed in from one room to the next affects room acoustics. With mainstream receivers, you spend time calibrating them for the room using Audyssey, so I rarely ever want to use multi-room audio if I am actually using music for anything but having it casually playing in the background while I am cleaning the house or something.
That being said, Apple had to offer multi-room because a lot of people listen casually and apparently like the idea of music playing all over the house as they are moving from room to room. Not really my style, but Sonos and others have capitalized on that market, so apparently it is a popular way to listen to music these days. As an example, you would tell Siri you want to listen to your morning blend playlist and have the same music playing in your kitchen, bath and bedroom. I typically just use the iPhone to move music to the room I want to hear it, but it requires you to carry around a device in the morning.
As for receivers with that ability, it was about being able to listen to music in a separate zone by just buying a new set of speakers rather than spending hundreds on another receiver. In many of the receivers out now, you can actually send a completely separate audio and video signal to a separate room. I use this at home because I don't want to buy components for every room if I can simply use the same components in my living room to feed zone 2.
