Coming in October for insiders and in November for all in the update, Microsoft has prepared a series of updates which they call an "additional set of experiences"
These updates are looked upon by Panos Panay, a vice executive president at Microsoft & chief product officer for Windows and devices as sort of makeup tests. They will consist of new additions with the biggest one being a tabbed version of File Explorer.

File Explorer received a UI makeover in the last update but the tabbed interface was missing which was expected by many users so it will come in following the next update.
The rest of the features that we will receive are an updated Photos application, Suggested Actions in the Windows Shell, Overflow menu for the taskbar, and improved Nearby Share.
The tabbed File Explorer interface is essentially File Explorer’s version of Sets, the tabbed window interface that Microsoft tested out several years ago. In testing, the tabbed interface proved handy for moving and copying files, and we’d expect the same once the feature formally goes live. The difference between Sets and the tabbed File Explorer interface is Sets allowed for multiple applications to be clustered together via tabs.
Photos app will include a “new photos-managing experience that brings a gorgeous gallery, simplifying browsing, finding, management and consumption of your collection of photos.” It will allow “easy backup to OneDrive” and a “delightful Memories experience.”
As for other features, nothing specifically was said except giving just some tips on what will they bring, it is obvious that File Explorer and the photos app were the main focus for MS in this upcoming update.