From Leftlane News:
Spied: Next-generation BMW Z4? Z6? Z8? Z9?
Spy photographers have snapped photos of a new BMW roadster in testing on public roads in Munich. The spies at KGP Photography believe the vehicle is the next-generation BMW Z4, while the team at Hidden Image say it's the forthcoming Z9 — a successor to the BMW Z8 and a competitor to the Mercedes SL-Class.
This prototype appears slightly larger than the existing Z4, but perhaps not large enough to be BMW's forthcoming Mercedes SL competitor. In November, Hidden Image said BMW was working on a successor to the Z4 that would be named Z6. The name change would reflect the new car's increased dimensions.
UPDATE: according to the Leftlane news update, this is the upcoming Z9
Spyshots:
http://www.leftlanenews.com/2007/01/11/spied-bmw-z9/