

There is an exclusive preview program that they plan to extend over time, and it will give players in the preview program full access to the update and what it entails. The team also claims that it will be easier to communicate patch announcements and casting votes for features.
Accompanying the addition of Windows 10, Xbox One will also be receiving Xbox 360 game playback with support for over 100 games, with more to follow after launch.
Update Sept/16: The first wave of invites to the preview program have gone out today! Major Nelson has stressed that there will be more opportunities and an expansion to the program later on so if you did not get an invite this time, you will still have a chance in the future.
Source | Podcast