It is not a new rendering engine. It is just one custom tag which makes WebGL texture of your HTML content and allows to apply shaders. That is it...
I was commenting on a hypothetical future for something of its kind, and that I think HTML content is not really the way to go to make shiny WebGL things, IMO.
To be a little more on-topic, yes, as an "apply shader to this semi-static div" it is a pretty cool thing :)