The Google Duo app is getting more seamless with other Google services like Phone, Contacts and Android Messages. A recent update revealed that a dedicated shortcut would be included in all the three mentioned apps to access the video calling service. So, you should start seeing small camera icons in these apps next to contacts that can be video called.
Now, we have v20 of Duo hitting stock Android devices and a teardown brings an interesting finding to the fore. The app is likely getting prepped to add a screen sharing feature. This would be a very useful feature since many users have been asking to add it to Duo.
There are some strings that suggest this may also be used to launch a Google Cast session and stream it on TV. However, the code also suggests the feature is not ready yet and it might take some time to hit the stable build.