I think WebGL/OpenGL will do nicely to create a game like Ikaruga (http://en.wikipedia.org/wiki/Ikaruga). It's probably one of the hardest, but most enjoyable games I've ever played and I think mobile/indie game developers will pull it off. If anything this opens up a new democracy in the previously restrictive world (if not outright closed as in iOS) game development for devices and consoles.
I think we're already going to see OpenGL ES 3.0 being implemented into WebGL within the next 2 years, and even if WebGL never adopts the full OpenGL (it has a lot of cruft anyway), keeping up with the OpenGL ES API's should be good enough (OpenGL ES 3.0, ES 4.0, ES 5.0, etc).
I was thinking the OpenGL ES will be the future most popular graphics API anyway (on any platform). It's just that Nvidia announcing full OpenGL 4.3 support for Tegra 5 kind've made me re-evaluate that. But if other mobile chip makers just stick with OpenGL ES, and WebGL does, too, then OpenGL ES should still become the most popular graphics API in the next few years.
It won't make it into asm.js anyway, but into the WebGL spec.
Why, did you expect AAA games on the browser?
One step at a time people, one step at a time...
Mobile games of the kind you get on an iPad, with 60fps are a perfectly good target for the web browser.
Very smart move IMO.
Edit: To clarify. To think that the devs here are interested means the Mozilla folks got the right idea.