This is great! The only reason I use SCSS is for the nesting. It should have been implemented 10 years ago, but better late then never.
Nesting is great to avoid selector repetition.
Custom properties (CSS variables) and CSS functions give us tools to avoid magic numbers and to encode layout relationships.
New sets of selectors and container queries let us decouple and re-use declarations more.
CSS Houdini gives us further power in extending CSS functionality.
Of course there are things that SCSS provides which are unlikely in the scope of future CSS proposals such as datastructures (maps) and loops to generate classes and mixins. But I can already imagine a world were those aren't necessary anymore for many cases.