Microsoft will begin rolling out the big Clubs and Looking for Group update to all members of the Xbox Preview program this evening, This same update was pushed out to select Preview members earlier this week.
Microsoft's Mike Ybarra posted the news on his Twitter account today:
Today, ~6PM PST we will throttle release the Xbox One Preview build to all Preview members. Thanks for helping us build Xbox! #Xbox— Mike Ybarra (@XboxQwik) September 8, 2016
The term "throttle" means that it may take a little while for this update to roll out to all Xbox Preview members. The update adds new social features to the console such as creating or joining Clubs and adding "Looking for Group" features. They should be released for all Xbox One consoles later this year.