There's a very natural upgrade path from Angular 1.x to React: start building new little components in React and patch them into your app in Angular directives.

There's a very natural upgrade path from Angular 1.x to React: start building new little components in React and patch them into your app in Angular directives. You can even apply the flux pattern to good effect within the directive while still making use of your existing Angular service infrastructure. Per Evans this would be an Evolving Order over a pair of Bounded Contexts.