Here's the bottom line:
Porsche earns a boat load of money for every Cayenne and Panamera it sells. The 911 and Boxster/Cayman, by contrast, don't produce nearly the same profit margins, so it's fair to say that an SUV and sedan are what makes it possible for Porsche to develop and build its sports cars, including the upcoming 918 Spyder. That's business, folks.
Motor Trend is reporting when the Cayenne receives a facelift in 2014, a plug-in hybrid version will also be offered.