One day, I will be able to compile my golang apps to work on browsers without losing considerable performance, multiple threads and concurrency. That day, I'll be very happy.
It's important to emphasize that PNaCl is a platform. We currently provide front-ends for C and C++, but nothing prevents you from writing your own, for your own language (or an existing one). As long as you emit PNaCl bitcode, Chrome will run it for you. The PNaCl bitcode has a definition here - https://developers.google.com/native-client/dev/reference/pn... - and we're working on making it more precise.
One day, the browser will be used again just for documents. That day, I'll be very happy.