Because they wanted to sync the angular version with the angular router version. Angular will have a new version release every six months but Angular 4 will be backwards compatible with Angular 2
- Angular is being developed in a MonoRepo it means a single repo for everything.
@angular/routeretc are in the same repo and may have their own versions.
- The advantage of MonoRepo is, you don’t have to deal with the versioning of the code dependencies.
- Now the problem is with the @angular/router which is already in a 3.X version. And that’s because of some active and huge developments on the router section, like route-preload.
- Now releasing Angular as version 3, with it’s route on version 4 will create confusion
- To avoid this confusion they decided to skip the version 3 and release with version 4.0.0, so that every major dependency in the MonoRepo are on the right track.