Cult of Mac has released a page where you can compare the icons of macOS Big Sur and the icons of Catalina side by side and see how they change.
Change to iOS-like icon
The icon of macOS Big Sur seems to change to an iOS-like one, but the Cult of Mac has published a page where you can check how the icon is changed by switching the icon of Big Sur and the icon of Catalina. I will.
With macOS Big Sur, it seems that the icon of the genuine application will be changed to a simplified one compared to the icon of macOS Catalina.
System Preferences icon
It seems that System Preferences icons such as Boot Camp icons will also be changed to “rounded” icons.
All of these icons are from developer beta, so the Cult of Mac reports that the icon design may change in the official version of macOS Bug Sur that will be released this fall.
Source:Cult of Mac
Source: iPhone Mania