I agree, putting one more layer on top of JS does not allow to do substantially different things. But I would argue that this is the only option. Google is pushing its PNaCl [1] clients where you can run C++ code in your browser independent of the platform. Isn't this partially solution to the chicken-and-egg problem? It may get adapted because there is a strong player behind it. It also allows substantially different things to be on the web. For instance you can run some heavy computer vision app analyzing webcam stream directly on client side. Apart from notable JS exceptions [2].

[1] http://www.chromium.org/nativeclient/pnacl [2] http://liuliu.me/ccv/js/nss/