The transition from SystemJS to Webpack is still work in progress, but the team is looking to make the change as simple as possible:
We want to make sure it’s ready. That’s why we need your help. Basically, things should work. Build and Serve should work. Also, testing and E2E should too. To put it short, everything should work as it was before. But we’re not certain! Test every commands you can think of. Use your normal work flows. We need you to test your projects and file issues about it.
Developers already using Angular 2 CLI should take a look at the migration pull request. In any case if you’re looking to start new Angular 2 projects using the CLI you should probably already start using the Webpack powered beta as that will spare you from migration in the future