The Xbox One Preview Program is being rebranded and will unlock the doors for everyone to participate, not just those who received a fancy invitation.
Called the Xbox Insider Program, fans will be eligible to receive future Xbox One Dashboard updates and various incentives for providing feedback to Microsoft’s services. Current members of the Preview Program will remain locked into the service when it changes but will encounter new changes to the program’s UI. Previously, the Xbox One Preview Program was only available to those who received an official invite from Microsoft.
In the past, Xbox One Preview Program members were given early access to the Halo 5: Guardians Multiplayer Beta, various dashboard updates, and the backward compatibility feature. It’s unknown if game beta’s and key features will still become a part of the Xbox Insider Program, but we are sure to hear more information when the program officially launches.
There is no release date on when the service will be rolled out.
Source: Xbox News Wire