Porsche has had this competition in the previous years, as a matter of fact two of those that you mention are new versions of previous exiting models. And cars such as the Dino or AMV8 are to low production to even matter.

Same old story herd all over again, but the truth is that the 911 is the benchmark and the king for over 40 years and current production numbers and sales show that its even better than ever! The 911 has its own niche, it has several generations of followers, and offers a unique package that is unmatched by any other manufacturer that appeals to a greater and greater target population. Other sportcars come and go, but the 911 is the greatest success in sportcar history and shielded from any market movements.

Were I see Porsche can have more competition problems is with the Boxter/Cayman platform, were they have no such things that the 911 has, many similar products from the competition, and a very changing and unprecitable buyer base in that segment.

And the 911 success does not mean that they cannot expand to other markets such as the SUV and now the 4-door saloon (the 928 was a 4 seater coupe not a 4-dooor saloon) much to the dismay of other car makers.