Google Assistant is always getting smarter and learning new tricks, but it doesn't usually need big user-facing updates to make it happen. You will, however, need to get your hands a little dirty for a new Assistant update if you're using any smart home devices. Google is sending out an email to Assistant users to let them know smart home gadgets will need to be relinked after the latest update.
The email is vague about what exactly is included in the update, saying just that it will enable new features in the future. In order to keep using your smart home devices (like Hue lights, Nest Thermostats, and SmartThings), you will need to manually accept the update. Unfortunately, that means unlinking and relinking all your devices and configuring rooms and nicknames all over again. See the email below.
The upgrade message will appear on your phone if an update is required, probably after you issue a command to one of the affected services. You can access the settings to unlink by going through either the Home app or Google Assistant, depending on how you connected the devices originally. Services that need to be set up again will have an "Upgrade" label next to them.
Some users are seeing the update message already, but it's not universal yet. Keep an eye out for the notification on your device soon if you haven't seen it already.