You can already use most simple web components in Angular without issues - as far as Angular is concerned, it's just another DOM element.

We also support native (or emulated) Shadow DOM out of the box.

It gets a little more interesting when you start interleaving Angular and WebComponents, but one of the deprecations in 4.0 (regarding Angular's use of the <template> tag) is squarely aimed at making that easier in the future.