Why was Angular 3 skipped, and what are the major differences in Angular 4 beta

Question

Angular is being developed in a MonoRepo it means a single repo for everything. @angular/core, @angular/compiler, @angular/router etc 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 its router 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.