As the Office preview is supposed to come by end of the month, so it may seem we will see this build arriving by end of this month. Check the video below. These are some of the changes one can notice in the video.
Build 10.0.12544.63 changelog:
Many more theme color options
Office universal apps preview
Supre fast Lumia Camera 5.5
Thanks Xio-Feng for the tip. Cheers!!