As far as I understand this at the moment only some Amazon Echo devices are affected by this. It’s done because Alexa+ functions can’t be used as a local service on the device.

So imo for now non Alexa+ Echo devices still will be able to use Alexa as a local on device service. 
But I‘m pretty sure that will change in future when Amazon is going to expand Alexa+ for other hardware. 
Regarding to Sonos devices Alexa always has been working via Amazon cloud service. 

Since Sonos doesn’t do any of the effort for Amazon’s Alexa on their speakers, but sends your voice to Amazon for processing, I’d think any change Amazon makes would be reflected on Amazon’s servers. Sonos doesn’t ‘own’ any of that. 

Sorry ​@Airgetlam … you are absolutely right, Bruce. As Sonos never did local Alexa operations these changes seem to affect only certain Amazon Echo users. I did edit my last post. 

We posted at the same time ;)