Although the Angular team already talked about migration paths in their weekly meetups, in early design docs etc…From total migration (i.e. complete rewrite), letting Angular v1.x and v2.x coexist within the same application.
Now it’s finally official. Brad Green, Engineering director at Google and responsible for the Angular team, now officially announced the possibility of having Angular 1 and Angular 2 coexist within the same application. That’s absolutely awesome as it allows for a sliding migration where you develop new components in Angular 2 and migrate older components as you have to touch them. This is a huge win 👍