What does that mean for Android users?
There are numerous video calling apps available but they are not really integrated in your native messaging app on your Android device.
"You can now start a video call directly from where you call or text message your friends, through your Phone, Contacts, and Android Messages apps". Charlston's comments would indicate so, but knowing Google's history of shipping devices, it's not a certainty; perhaps call ahead if you're thinking about making a trip. Google needs to finalize some things first with different device makers and mobile carriers for the integration to be ready in more phones.
The Google Pixel 2 and Pixel 2 XL are edging closer to their official release. As for other devices, Google is nudging its partners to update, but it's up to the individual manufacturers to decide when or even if it's worth doing.
If both the caller and the recipient are on a carrier that supports ViLTE video calling, the calls will be routed through the carrier's ViLTE service. Some communication apps have integrated with Google Duo for video calls but it's only now that the Android team made video calling part of the messaging feature. In Contacts, you will notice a Duo video call icon has also appeared, while in Android Messages app, you can start a call straight from your chat.