Our stack is primarily in Java (Spring MVC), with frontend in Angular 1. We were thinking of moving to Angular 2. But, the recent announcement of Angular 4 made us wary. And now, we are contemplating waiting for Angular 4.
How similar Angular 2 and Angular 4 are likely to be, according to you? Would you advocate we spending efforts on two upgrades - or just one big one - from angular 1 to angular 4?
No need to wait or afraid of V4. This is not a re-write like it was with AngularJS 1.
The Angular team switched to semantic versioning http://semver.org/ and will schedule a major release twice a year: V4 in March, V5 in September etc.
They're adding new features and might introduce some breaking changes, but the impact on your existing Angular 2 app will be minimal.