Bearing in mind they're adding the Cajun (mini-Cayenne) soon, I'm guessing they're not too interested in other markets right now. In all honesty (and being completely biased I will freely admit), why should they?
You want a roadster? Buy the Boxster.
You want a small coupe? Buy the Cayman.
You want a 2+2 practical sports coupe? Buy the 911.
You want something utterly balls-out? Buy a 911 GT car.
You want to ferry the kids around? Buy the Cayenne.
You want to impress your golfing buddies? Buy the Panamera.
There is no other car company barring Audi that have such a broad range of sporty cars that are all dynamically at the top of the tree (which is where Porsche beats Audi). Anything else just isn't necessary and would dilute the brand further. Bearing in mind the 928 was supposed to replace the 911, but no-one bought it in the numbers they expected because they all still wanted that gorgeous shape mated with an unusual drivetrain and the howl of a flat-6. Sadly, there's a reason that Porsches are incredibly common, but that's because they're all so bloody good.