Microsoft may still be able to hinder the web by using its influence in W3C to push for detrimental standards like Encrypted Media Extensions, and by refusing to implement things like WebGL.
Microsoft can slow the adoption of web standards (and just via the desktop), but they don't have any real control now. And the only reason WebGL isn't in IE 10 is because they didn't want to offend the DX/D3D team. Once IE supports WebGL, D3D will die.
On the bright side, I've seen rumors that IE11 will support WebGL, but that is of little use to people stuck on XP, Vista, or W7 due to compatibility requirements of other legacy apps. As you say, IE doesn't have the dominance it once did, but for some reason it's still used in certain market segments.