Yeah the alternative future where NaCL reigns and you can program in any language you want, compiled languages, like C++, C# and interpreted/JIT/AOT like JS , Python etc would be awesome. It's already a reality in some extents. There's quite a few games using NaCL on Chrome Web Store. The problem is that Chrome holds total control over it at the moment :( But the advantage is that you have the same power of desktops. It performs much better than WebGL and Flash 3D, and ideally will run everywhere.
One thing i believe: It won't stay how it is now.
The obvious tendence is to desktop domain to fuse with web domain. NaCL is the first real step towards this goal. Chrome please open source NaCL !! But that's the future.
The money now is on: Social Games on browsers and Mobile Games of every kind on iOS and Android. End. C2 already covers in an extent the first one. So it's surely in the right direction.