Vue 3.0 will use the Proxy API to power its reactivity system. It will improve its performance and remove all the reactivity system limitations.
For example, you will be able to do this.myArray[1] = 'new_value' and Vue will detect this change and update your components automatically. Adding entirely new properties will work too. As a result, Vue.set will be deprecated.
It will also allow performance improvements for large arrays, and lazy reactivity conversion will make using big datasets faster.
Currently, we foresee one possible breaking change: Vue will use Proxies for the values accessed on the component instance, so equality checks with the original values will fail.