The Angular team has released Angular 4.0.0-RC.1. This is a feature complete pre-release version. As per the announcement, Angular 4 will be released on March 22, 2017 and it will be backwards compatible with Angular 2.
https://docs.google.com/document/d/1rC5dz7AkCZP813daT_bccbS-20OLmXgBVi50CSKx148/pub
Happy Coding!