Audio from any iOS device can now be sent to multiple Sonos devices. A free software update is being beamed out today, accessible through the Sonos application.
As well as multi-room audio, customers will be able to use Siri to request music on Sonos via Apple Music. However, this will be via your iPhone or iPad - none of the devices are getting Siri natively in the same way the HomePod does.
The company has also said Google Assistant is coming to the platform as well (which will probably mean Chromecast compatibility), at some point in 2018. It's likely that this will put Sonos ahead when it comes to smart-assistant compatability - but we'll have to wait until it happens before we can judge.
Unfortunately, while Sonos is happy to build its multi-room services, it's unlikely to update them to support three-dimensional audio processing like Dolby Atmos or DTS Virtual:X.