Have installed the 8.1 preview, and IE 11 has webgl (flagged as experimental).
However when you create a win8 app it still uses Canvas2D.
We wait and hope......
Yeah...I might have to ping the dev who gave the talk at the BUILD conference. They might not have enabled it fully. I really need this to happen, I only have windows phones at my house and I want to test my game with WebGL because it uses a good deal of physics.