Lots of controversy about this one. Is this a new model from BMW (Z6?) or is it merely a new version of the Z4?
The question arises because this is obviously bigger than the current Z4 (which itself was bigger than its predecessor the Z3). BMW is also expected to be working on a smaller roadster based on the 1-series car.
There is also an expected roadster meant to compete against the SL from Mercedes.
Given that BMW is expected to stick with even numbered models for the roadsters...I'd expect the 1-series based model to be dubbed Z2, this car to be the new Z4 (bigger only to make room for the Z2) and then the SL competitor to be the Z6 (and, as yet, unseen).
Additional confusion has arisen from the fact that this car has been seen with a retractable hard-top, but this would make sense for a mid-range luxury convertible (expect the Z2 to have a fabric roof).
Read all about it at:
WorldCarFans.com: Spy Photos: BMW Z4 with Roof Down