Dolby demos Dolby Digital Plus
"Dolby Digital Plus ... supports 13.1 channels."
Yes! Triskaidekaphonic sound! Finally!
Let me see, now... in addition to the subwoofer, the current max, 7.1, has 3 front, 4 rear. Perhaps this adds 3 right-side and 3 left-side speakers? Or maybe 3 front, 3 rear, 3 right, 3 left, and one more "top" speaker right in the middle of the ceiling? How about splitting the front/rear sets of speakers into "upper" and "lower", plus an extra one, say, under your chair?
Or perhaps just 12 evenly spaced around the listening area in a dodecahedron, plus one more you wear on your head like a hat, for, y'know, internal monologues and narrators and things like that.