I think that the omission of Microsoft is rather deliberate; this is the next phase of the browser wars. Hopefully there's enough of an installed base of sites that work with WebGL that when Microsoft launches it's catchup version it's as much of an epic flop as WindowsME.
Or Microsoft could get on board and not attempt to piss in the pool yet again; stranger things have happened.
Actually, I don't think Microsoft cares that much about their browser. It's not like it makes them any money. It was a selling point for their OS. Now there are plenty of alternative selling points.
Microsoft will have to get on board. It's pretty much a given that this will go in the Chrome OS, so I can't imagine MS just letting google check off that feature.
Not diasgreeing with your main point (that MS will have to go with the same standards as everyone else), I think you wastly overestimate the importance and impact Chrome OS will have.
Chrome OS will be the most niché OS ever, just slightly ahead of Linux in the client-market.
Or Microsoft could get on board and not attempt to piss in the pool yet again; stranger things have happened.