Update 11/3: The official changelog for Messenger 2.0 has been posted and it reveals several new features. There is a slightly redesigned photo picker, unread badges for the app icon on supported launchers, and Nougat support. Notably, RCS receives its first official mention for “some carriers”:
Enhanced features that let you send messages over Wi-Fi or your data network, see when friends are typing, and more.
Compared to Hangouts for Android, Google Messenger is quick to add support for the latest system features. Messenger has just been updated to version 2.0 with a new icon and redesign that matches the general look of the Phone app in Android 7.1.