We're using AngularJS on a large project, and although we haven't looked deeply at Dart yet, I still have a ton of questions in regard to their future compatibility, potential overlaps, roadmaps, etc. I've seen some message group posts about this, but there was nothing definitive and the core groups don't seem to collaborate at all (please correct me if I'm wrong).
Definitely check out Web Components. It's aiming to take many of the low-level features of the MV* frameworks, like templating and data binding, directly into the browser. Angular was created with a "what would HTML look like if we could extend it" idea, and Web Components is the "ok, let's add it to HTML now" response.