Microsoft will be pushing Windows 10 Build 16199 and Windows 10 Mobile Build 15125 to insiders in Fast Ring. This has been teased by Dona Sarkar in her trademark style on Twitter.
Look closely in the tweeted image below and you can notice those two Build numbers. Hopefully Windows 10 Mobile Build 15125 may be the first build that brings some noticeable changes.
— Dona Sarkar @ #MSIgnite (@donasarkar) May 17, 2017
You can check what changes has been brought by all Windows 10 Fall creators update preview builds till now by clicking here.