The Main issue I would see from apples POV for 'running windows' is support.
driver doesn't work, or XYZ crashes, ect, THEY'RE going to get the call to support it. and it wont be the wonderful Genius Bar experience, when they have to say 'we dont know, contact the app developer, or windows, or ...' so they ship a few more units, I dont think at the price / margin level of the machines apple sells, they want to take on that responsibility, there's just not enough ROI.
can it work, sure. throw it out there, let the crazies run windows, they're just not going to support it like its OS X