A new Preview Beta build (1706.170728-1839) has begun to rollout to Xbox One users enrolled in the Xbox Insiders Program. There don't appear to be any major changes with this build beyond some game installation and Party Chat fixes though. Here's the official release notes:
HOW TO GET IT
If your console is in Instant-On mode and you have been selected to receive the update, it will download and install the update and reboot to standby.
NOTE: Once the update is available to you, you can manually begin the update by launching the Guide and navigating to All Settings > System > Updates.
If your console hasn’t downloaded and installed the update by 1:00 AM PDT 8/1/2017 (8:00AM GMT 1/8), you will be prompted to do so at that time.
This update has a shorter than usual window before the build becomes mandatory.
OS version released: rs2_release_xbox_1706.170728-1839
Available: 6:00PM PDT 7/31 (1:00AM GMT 1/8)
Game Installations: Fixed an issue with Game Installations that contain multiple languages in which the game can launch in the wrong language.
Party Chat: Fixed an issue in which some users are being disconnected at regular intervals with improved error reporting.
Preview builds like this are used to test software changes and new features before they're rolled out to the general public userbase. Have you installed this build and noticed any other changes? Let us know in the comments below.