I heard a rumor that the shield might also use motion plus. Actually I just made that up, lol but isn't that what a rumor is? anyway I think it's highly likely that the sword won't be the only thing to incorporate the new motion controls.
In a interview with the Zelda team they plan on using the Wii Motion Plus to include things such as sword play and possibly shield action. This isn't confirmed, but it is a common theory with the discussion of the Wii motion controls.
I heard a rumor that the girl on the official art is not the Master Sword, but will be included as a main part of the plot.