They say it will be gone by the end of the year. Another thing is Sonos has moved parts of system to their cloud. It’s unclear how a system will perform  if internet access is not available. It seems like it will work ok but perhaps not the same as 16.1. Something to watch for. 

So the entire "upgrade" is actually them switching to a cloud web based system. Ugh. It's worse than I thought. I see it now. 

Sonos won’t say this loud probably, but people without regular internet access are no longer of interest to Sonos as a market. It is a complete reversal of how Sonos started, but the reality is that the profile of their user base has changed in the last two decades with the widespread and reliable availability of the net. 95% plus Sonos users do not use a local NAS for music, they use streaming services and internet radio.

If your Sonos kit has line in jacks, don’t discard that in a hurry! There are lots of ways to use it to play music, with and without net access.

95%? That's crazy. 

I do listen to internet radio, but I really like my own Playlist and queues. Radio gets repetitive fast. I suppose I can make the line in work, but then I would have to move speakers around, and then only control it from my computer which is upstairs, seems like a huge downgrade. Plus then, my kids couldn't play their music in their rooms! Very disappointing! Maybe they will do like the S1 app again for the old geezers.

They are talking like a Plexus thing where you have to upload all your music for a fee, but I am not too sure about that. Seems troublesome. 

I refused to budge from S1 in 2020, so I am ok...so far. And they really should leave S1 and a path back to it open for those that stayed on the Sonos bandwagon in 2020. 

If it turns out that you don’t get that and are unable to reach your Sonos units via a web app for lack of the web, you are left to use devices like the old iPods that have a audio out jack and wire connect them to the line in jacks on the Sonos units - to the extent of those that have these jacks.

How could you control your speakers from your computer today, if you only have a web app? Perhaps the web app will let you do that in future, but by definition a web app needs the web.

I meant that I could use my computer as a line in, and use Windows Media Player or other program to control it. I have a play five with a line in, that I could move. But.... I would look at other options first, and sell my Sonos speakers, since that's a pain in the butt.