Look at this thing, who's betting on how much it costs? more than XO?
edit: also, because the new design puts it closer to the wheel, although that outside hit from a rock may not hit it dead on, it may be enough to push it into the now very close spokes.
http://www.sicklines.com/2007/06/15/2008-shimano-xtr-shadow-rear-derailleur/#more-1501
Also, on the front page of sicklines, they have a post on the Banshee Rampant 4X, looks really nice. the lettering reminds me of Nicolai.