The current 997 generation Porsche 911 is still being updated for its mid-cycle refresh, with only the standard Carrera, Carrera 4, and Targa variants receiving the update. Still in the works are the new Turbo and the GT3 models, though they too are drawing near to their expected unveiling.

Recently a test mule was spotted in Germany by our spy photographers, suggesting that Porsche engineers may have already begun testing the next-generation 998 model, and now we have a new images of a prototype for the upcoming car. Note that the side vents on the car are fake.

Clear differences between the 998 and the current 911 model are a pair of more upright headlights, a slightly longer body, and the side mirrors are now positioned at the side of the doors and not at the window.

It’s still too early to determine what changes Porsche has in store for the engine lineup, but expect to see the recently revised flat-six engine range carry over with only minimal updates – possibly for emissions and economy standards. The new PDK dual-clutch gearbox will also carry over as will a standard six-speed manual.

The next 911 isn’t expected to arrive in showrooms until late 2011, but we expect to see much more of the car from spy photographers as it develops.

Also in the works is the next-generation Boxster convertible, which you can see a prototype for by clicking here.