After the reveal late last year, in which Windows announced a new set of icons to represent a new era of Office; Microsoft is updating the icon for OneDrive Desktop sync client for users who have opted into Insider preview builds.
The update also brings support for Windows 10’s new light theme introduced in version 1903. There are also bug fixes and various improvements so the app runs more smoothly.
Despite no mention of this in the official release notes, new icons can reportedly be seen in version 19.073.0415.0001 of the OneDrive sync client. To get that opt into Insider Preview builds by ticking the box in the About tab in the sync client as shown in the screenshot above.