The problem with shooting movies at 48fps is that you have to change the way movies are made. Traditional methods don't work any more, because you can see it for what it really is and not what you're creating the illusion of.
24 fps in movies is slow as hell, thereby you can make shit look good.
Even with shooting in 3D, you have to change the way you shoot. Action senses look very fake in 3D with traditional methods, in 3D the viewer can see that it's fake, so a punch has to make contact or the view can see that.
anyways, it's pointless to produce animations over 30 fps.