Gabe Aul has just informed that Windows 10 Mobile Build 10536.1004 is looking good so far under testing and if it remains so, tomorrow morning Fast Ring Insiders can expect it to hit their devices. Build 10536.1004 looks like a minor upgrade (version number wise) over the Build 10536.1003 that was released to some Insiders by mistake. You can read all the changes that the Build 10536.1003 brings by clicking here.
Mobile build update: We deployed 10536.1004 to our final Microsoft ring yesterday @ 4:00. Data for ring promotion is looking good so far.
— Gabriel Aul (@GabeAul) September 14, 2015