I think you should look at a timeframe also. If you write an application today in Angular 1.x you could probably contiue to use it for about 18-24 months. It is really hard to know which frameworks will still be maintained in 24 months time and it is not unheard of rewriting the application anyway after that time. As for the actual rewrite from Angular 1.x to 2.x I think Google will create scripts that help with the rewrite making it go much faster than 6 months. They actually have a LOT of internal applications written in Angular 1.x and would probably not want to spend the whole of 2016 rewriting everything.