One of my favorite features with Google Assistant is that when I have more than one speaker with this virtual assistant in different rooms, I can use it like a walkie-talkie or broadcast announcements. This is because they can communicate with each other easily.
The Matter standard, which tries to make the ecosystem of various Internet of Things devices into a single system, tries to do this. Slowly, Matter now supports various products from doorbells, washing machines, water sensors, smart lights and more. In the future, the Matter standard will also support audio streaming to speaker products.
The idea of Matter is to make this feature universal. For example, receiving a doorbell from the Nest Doorbell - an audio notification can be delivered to the Amazon Echo or Apple HomePod. Or, the Samsung washing machine is ready to wash clothes - the Nest Hub can play music as a reminder. It is different from existing products that use the Matter control system rather than products that control/access other products.
However, in my opinion, this feature will not be used by device manufacturers for their audio product ecosystem. Again features like multiroom, multipoint and others. Google, Apple, Sony, Devialet, all have their own ecosystem and do not utilize the universal ecosystem like Auracast.
Let's all look forward to further developments for Internet of Things devices under Matter. Who knows, there will be small brands that can bring a complete ecosystem like Google Home but with various products from different brands.