It would be fantastic if IE11 supported WebGL, but I wouldn't take this news to be confirmation in any way. The evidence comes from a leaked version, which MS didn't want to be public. So it may be that MS engineers were simply doing some kind of experiment which they'll later remove, but their experimental version got leaked. Even so, the fact they're at least experimenting with it is interesting.
MS appear to be getting in to a very difficult position with WebGL. Unreal Engine 4 supports WebGL, which was announced recently; some popular games like RuneScape have announced they'll support WebGL; we've always supported it and have pointed out its rendering and performance benefits. So if they continue to refuse to support it, more and more people will switch to other browsers for gaming. But supporting it would probably seriously hurt Microsoft's own DirectX, which they have a big interest in pushing. It would also be embarrassing for them to U-turn over their previous "it's insecure" nonsense they tried to use an excuse previously.
Whatever happens, it will be very interesting to see what they do about this.