Actually, 3D may actually have something to offer...
With 3D, since they have to double the graphics output, it makes local co-op easier to do. It won't be co-op in 3D, but hey.
There was also a method patented a while ago for local co-op using 3D glasses a while back as well...
Nice to see a throughly researched article
Looks like co-op might actually be making a come back