The only thing I found at Fortune online was this video, which gives some good insight to the original poster's question:
http://money.cnn.com/video/ft/#/video/business/2007/07/12/fortune.global.500.porsche.cnn
I did find a Forbes article, which says Boxster sales are down 21.5%:
http://www.forbes.com/2007/11/30/cars-sales-year-forbeslife-cx_bh_1130worstcars_slide_8.html?thisSpeed=30000
21% is along the lines of the data I have.
Not trying to nit-pick, just trying to verify my data as I have some analysis to complete for the 'real world' and I didn't want to be completely off the mark.
And in answer to the original question, if Porsche likes to keep their margins above 19%, they'll clearly have to do something about the Boxster - Limit production, spice the car up with a limited edition, or drop it from the line. It looks like the first two options is where Porsche is headed for now.