While HTML5 hasn't been employed heavily by the gaming industry, signs of it are showing up. Gas Powered Games' recently teased "Project Mercury", their next-gen cloud powered Modding Tool & Web platform – http://youtu.be/kuGdQqUhKD4

Such projects are possible only due to HTML5/WebGL, and the innovations on top of it. In a couple of years, we'd be seeing mainstream studios shipping AAA Games as Web-based applications.