Unfortunately that proposal seems to be kinda dead.

React is a fundamentally flawed framework because of the lack of this feature. It inverts the responsibility of any non-primitive prop by putting the burden on the parent element instead of the child to decide when to rerender things. So elements are no longer self-contained if they receive any non-primitive values (besides react elements).

The React compiler auto-memoization that facebook is pushing also addresses this issue through build-time magic. I not fond of this approach.