To avoid too much anticipation I'd like to make sure you know that there will not be any new content in the new patch other than the VW Scirocco.
Anyone who is not a programmer would probably be surprised how much time some things took to improve, such as the new wheel drawing system and the updated car shadows. The graphical detail of the Scirocco inspired graphical improvements that had to be implemented along with various optimisations to maintain efficiency with higher detail and that just takes time. I can confirm that only the VWS and FBM wheels have been updated to use the new wheel modelling system at this point.
We've also been working on other new things which have not been announced and will not be released in the near future.
So... it'll be a nice patch with some noticeable improvements and the new car, but not really representative of the amount of work that has been done since patch Z.