Microsoft is very dominant in games because most PC games require Windows. If WebGL were to really take off/become a popular way of distributing/consuming PC games, which would be 10 or 100x more likely to happen if Windows supported it out of the box via Internet Explorer, you would have to expect to see lots of relatively inexpensive and even free 3D games that run in the browser, and take little or no time to install.
Even with Microsoft refusing to support it, now with Pointer Lock API coming very soon to a regular Firefox release (tomorrow??) and probably Chrome soon also, it will be possible to release a FPS or MMO on a website with native browser technology. Throw in the momentum and capabilities of Node.js, and I think that means choosing a web stack has big advantages as far as ease of development for a lot of multiplayer 3D games.
I also think that where JavaScript/JS-based languages like CoffeeScript are really going to shine and be popular is in scripting for multiplayer 3D environments online.
I think that mainly we are just waiting for Pointer Lock, maybe a tiny bit better collaboration between browser and driver developers, and some social momentum.
When WebGL takes off, Microsoft Windows sales will take a big hit because people will be able to play the popular games on Macs or even on Linux machines.