Microsoft is rolling out a new build for members of the Xbox One Preview Program today, bringing the build string to rs1_xbox_rel_1610.160929-1900. There aren't any new features listed in the release notes (we're still waiting for Arena), but it does contain a number of fixes, and one known issue with Clubs.
Here's what got fixed:
Sky TV, Now TV, HBO GO
Resolved an issue which could prevent users from playing content in the following apps - Sky TV, Now TV, or HBO Go.
Resolved an issue which sometimes caused stuttering when playing a game with a snapped app.
When receiving voice messages from another user, you should now receive a notification.
Resolved an issue which caused description tiles for most recently used games and apps to appear solid instead of transparent.
Here is the known issue:
When viewing Clubs, you may still see the option to start a Club Party even if you are not a Club member.
While this is a preview of a feature update - which first arrived four weeks ago - it's worth noting that this is not Redstone 2, as you should be able to see from the build string. Instead, this is the second part of the Anniversary Update for Xbox One, the first part of which arrived back in July.
Today's build is slated to begin rolling out at 2 PM Pacific Time, or 5 PM Eastern Time. As for a public release, we can assume that it should be available this month, as the version number (1610) would indicate.