The newest version of the official Google app doesn't bring much in the way of user-facing changes, but an APK teardown that the app was treated to courtesy of the XDA Developers community revealed a wealth of new features that may be making their way to the app in the near future. The biggest change that seems to be on the horizon is the ability to register multiple voices for hotword use, which would not only imply easier device sharing, but perhaps an end to Google Home commercials making your devices jump to life. The code also references a "Rating Service" for Google Apps and certain services, and a mysterious device called "Bisto".
The bits of code pointing toward multiple users for hotword detection are phrased "Hotword Enrollment Multi-User", and seem to be part of a whole new setup process, which means that the feature will likely walk each user through the process of registering and training their voice. It is unknown what the implications here are; perhaps other users could use Google Assistant with their own account on a shared device, or a device may only respond to registered users saying OK Google. The rating system is a bit more mysterious, seemingly tied to a rating widget, apparently there for services in Google Assistant or Google Apps.
The most mysterious bit is the reference to a whole new device type. The "Bisto" device is referenced multiple times in the code as a device that Google Assistant can run on, but beyond that, the code is pretty vague. The prompts seem to mention headphones, which means that Bisto could be something that would require headphones, or some kind of audio-based smart hearable with Google Assistant on board. It goes without saying that all of the code found and detailed within the APK has not gone live, and it's entirely possible that Google will choose to simply keep it inactive, or delete it entirely in future releases of the official Google App. On the same token, these features may all be coming into the fold in the near future; the code is refined and elegant, and the bits that are present seem ready for primetime.