I had a discussion today with my BMW salesman. I have known him for almost 20 years and he has never given me any really bad information. That said he admits that BMW USA often give them the mushroom treatment. This is what he told me he is being told by BMW USA about the future of the Z4. He is also aware of all the rumors going around the web and in the various forums.
Current models will continue until mid 2009 with 2009 models basically unchanged from 2008 models. Roadster production will then move to Germany with 2 models for 2010. An upscale Z4 meaning a little bigger and more expensive and with a V8 as an option. A smaller roadster based upon components from the Series I (I guess that would be the Z2 we have heard about.)
I asked about the issue with the S54 engine not meeting 2009 emission standards and he told me he was not aware of that issue. Anyway it will be interesting to see just how accurate this is in a year or so.