Microsoft released KB4020001 and KB4020002 Dynamic Updates Windows 10 Version 1703 for x64-based Systems.
This updates makes improvements to ease the upgrade and recovery experience to Windows 10 build 15063 Version 1703.
KB4020001 -- Compatibility update for upgrading to and recovering Windows 10 Version 1703: April 25, 2017
KB4020002 -- Compatibility update for upgrading to Windows 10 Version 1703: April 25, 2017
KB4020001 makes "improvements to ease the upgrade and recovery experience to Windows 10 Version 1703", KB4020002 changes "the upgrade experience to Windwos 10 Version 1703.
Both updates are listed as critical updates, and offered as CAB files right now on the Microsoft Update Catalog website.