They'll continue working together if and only if you never update the software on the newer devices in your system ever again.
“Half house audio” is the new hotness.
“In May, you’ll be able to decide if you want to keep your legacy devices operating with your modern devices, and you’ll be able to put them all into a non-updating legacy system”
So they are actually reversing course to a certain extent.
If there’s one thing Sonos has shown throughout this mess, it’s that they’re really quite poor at communicating things clearly.
[0] https://en.community.sonos.com/ask-a-question-228987/questio...