I think the Cayman was a mistake, especially since it is actually "only" a Boxster Coupe but Porsche wants to sell it as a product "above" the Boxster but "below" the 911.
In my opinion, the Cayman will seriously hurt 911 sales, more than Boxster sales.
It would have been a different story with 380 HP in the Carrera S and 350 HP in the Carrera 2 but considering the much better weight/power ration of the Cayman compared to the Carrera 2, I'm afraid people will choose the better performer. So far, I heard that the Cayman S is close to Carrera 2 performance and on the track, well...