I think that's for all Z4 models. I remember seeing stats for previous years where it was just over 3k sold per year. Anyways, I think the new engine is quite good personally.
I too share rking's concern that BMW will just chop the line if the sales drop too low.
Audi R8 V10, 6MT, Ibis White/Black with Red Contrast Stitching
Z4 sDrive35i, 7DCT, Alpine White/Coral Red [Retired]
335i Coupe, 6MT, Space Grey/Coral Red [Retired]