Scala can be very good at interop - I still use Wicket (Java) for my Scala web UIs. And I'm confident that the Scala.js folk will have a good answer for doing UI, whether that ultimately means Angular 2, another existing framework, or a native Scala.js UI framework.

All that said, if you're thoroughly committed to Angular 2 (a mentality I don't really understand - I love Wicket but if an equally OO framework existed in native Scala then I'd use that instead) then using anything other than Typescript is probably an unnecessary risk factor.