The last time Porsche was in trouble, their lineup consisted of the 944, 911 and 928. While the 944 turbo S was an amazing car, from the outside it looked like a 924 (which had been around since the late 70s) with fender flares. Same deal with the 928. It came out in 1978, received periodical improvements in displacement and trim but for the most part it was the same car. The 911 carried over most of its body shell for the better portion of 35 years.
The 968 came out which was essentially the same thing as a 944 S2 but with a front end from a 928 and some new taillights. The 993 came out which was yet another evolution of the same old 911 body shell. These products didn't turn around the brand.
The Boxster was the sole reason that Porsche had a turnaround because it was the first time in a long time they showed they could actually make a modern car instead of an evolution of something that had already been around for 15 years or more. Not to mention the water-cooled engine, which was the first Porsche use of one behind the passenger compartment. The 996 came out shortly thereafter and was a huge departure not only because it was the first time a 911 had new windows but also because of the water cooled engine. The 944/968 and 928 got killed and Porsche sold its new interpretations of the 911 and Spyder.
The problem now is that even though in the Porsche scheme of things the Boxster and 996 are still pretty new, they've been pretty static since they were brought out. Unless there's another pretty big shakeup, Porsche isn't going to be able to attract the attention it needs to its sports cars that would creat sufficient sales.
As for the Cayenne, I don't have a problem with it. Sure the concept of a Porsche truck in and of itself is pretty much heretical against the purpose of the marque, but I don't plan on buying one. Porsche had a relatively minimal investment in the program because it was shared with VW, and the good sales numbers keep the company afloat until they can regroup their sports car operation and make it profitable again.