I would have thought the time that IE could effectively hold back the web had passed.
Even if they were on board with WebGL then I assume we're talking support in IE10 released alongside and quite possibly restricted to Windows 8. It wouldn't be crazy to think that IE, across all versions, would be down to 25% marketshare at that point and their mobile marketshare is basically non-existant.
IE's outmoded release schedule means that they can't really help or hinder the web much with decisions they make today. Certainly not compared with the damage they do by having old versions hanging around.