The Port.

https://www.sonos.com/en-us/shop/port.html

Hold on, the port doesn’t have optical which my  active speakers use. What then?

Get a converter.  Like this:

Coaxial to Optical Digital Audio Converter

Very poor- I don’t understand the consequences of NOT replacing the older devices. 

1 if I don’t care about any new features, will my system continue to run as it does now?

2 if at a later date I add newer devices (eg a pair of Sonos play 5s) will the system continue to operate? Currently s/w updates are in effect mandatory, and I buy a new item at say release x+ 2 and my existing system is at x -1 release? What then?

1. Yes -- but -- If a Sonos partner requires newer software to access their service it may no longer work for you.
2. I haven’t seen this addressed.

I also have a ZP-90 and received an email stating it would not be supported after May, 2020.

The email said the following regarding a mix of supported and non-supported system components:

Please note that because Sonos is a system, all products operate on the same software. If modern products remain connected to legacy products after May, they also will not receive software updates and new features.

No optical on port.  Therefore it is not a compatible replacement.  What were you thinking.  Not gonna buy a replacement that is lower res with no new functionality and then court the digital signal even further with a “converter”.  Wow. Will go to Bluesound or Audiolab 

A coax to optical converter is fairly inexpensive so I didn’t worry too much about the missing TOS socket on the Port.

I’m not sure why I get an email saying best answer by jgatie! This issue isn’t answered on the thread it’s a load more questions!

Yup… don’t consider the optical adapters a satisfactory solution.  I’ve already invested in high quality Toslink and a reclocker and don’t want to further mess with the signal (whether I’m drinking snake oil cool aid or not). 

 I’ve accepted the connect as a solution in 2 systems (ls50w and integrated/dynaudio systems). The reason is that any compromises in sound quality had to be balanced with the Sonos convenience and inclusion of native Pandora (which my wife has to have… bluesound Bluetooth isn’t a real Pandora solution). So until Bluesound or some other mfgr comes up with a reasonably priced product that sounds better and does hi res, includes tidal/Qobuz/PANDORA, and streams natively without casting through my tablet I’ll stick with the connect….. at least as long as it works.

There are some products like audiolab that seemed like they’d meet my criteria until I realized they stream through your tablet and cast to the device (Heos and others do this)…. really?  If anybody knows of an affordable product that meets my list of needs lemme know and I’ll take 2 today.

My opinions for what they’re worth.  Maybe ill informed but I’m tiring of looking for the unicorn and hoping somebody comes up with a product that meets my criteria before the connects stop working.