The guys at quattro GmbH in Neckarsulm told me Monday when I was there that right now the are just 'a studie' and they would 'soon be available'...
I'm going back to Neckarsulm tomorrow for a personal R8 production tour. Perhaps I can find out more then, but I thought you may have some other information.
John Stahmann
AudiWorld Contributing Editor/Moderator
2008 RS4 - Imola Yellow/Titanium

Previous Audis:
1975 Audi 100 ls
1998.5 A4 1.8T quattro - Brilliant Yellow
2000 Neiman Marcus TT
2000 TT 180 quattro - Silver
1999 A6 2.8 quattro - White (Stolen)
2000 S4 - Imola Yellow
2003 A4 1.8TQ Avant - Atlas Grey
2005.5 A4 2.0T quattro Sedan DTM - Light Silver/Black
Bonneville 130 Club member 2001
Bonneville 150 Club member 2007