As time has passed, we've seen Google slowly become more serious about a cohesive design language when it comes to Android, Chrome OS, and the Play Store. Taking one more step along that road, the company put out new app icon guidelines for app developers. This is meant to ensure uniformity in the Play Store and it will hopefully make it easier for you the user to have adaptive icons in your app drawer.
Starting in early April, developers will be able to upload new icons that conform to the new design in the Play Store console, which marks the beginning of the transition period. As of May 1, Google will no longer accept icons that do not meet the new standards, and by June 24, all icons that have not been updated will be converted to legacy ones. This is to ensure a consistent experience across the Play Store.
Left: Original icon; Center: New icon; Right: Old icon in legacy mode
If you're curious about the exact specifications, be sure to check out the second source link below. Google notes that only the Play Store on Android and Chrome OS will show these changes – mostly just applying a corner radius 20% of the icon size to maintain consistency – whereas Wear OS, Android TV, and Android Auto will not be impacted.
Again, this does not have any affect on the icons in your app drawer. This is simply to make sure that it's easier for you to get adaptive icons in your launcher and to enforce uniformity in the Play Store, even if Google has to use legacy icons to accomplish the latter.