Audi’s product expansion continues unabated, with a so-called four-door A7 coupe in the wings, followed by the next-generation A8.

The A6-based A7, as shown in this computer-enhanced shot, will give Volkswagen’s luxury marque a competitor for the likes of the Mercedes-Benz CLS. Dramatic styling touches include a chopped roofline, an aggressive nose design with a radical headlight treatment, and the rear door handles hidden within the C-pillar supports. Sources say the A7 should arrive sometime in 2008.

On the heels of the A7 comes the next-gen Audi flagship—this one deriving power from a V12 diesel and a new V10 gasoline engine. Early prototypes indicate the car is about four inches longer than today’s A8, reaching an overall length of 200 inches. Audi is busy developing the 2010 A8 in preparation for a planned launch in late 2009.

Audi of Ingolstadt will release this fall a concept car for the upcoming new Audi A7. Although the production version is not expected to be due before 2009 - first mules of the four door coupe have been sighted taking repeated laps at Germany’s race track Nürburgring. The prototype can be distinguished from its wider fenders, bigger tyres and expensive alloy wheels - painted black. The production car will get a luxury style four seat interior, frameless doors, a glass roof, and offer a choice of six different fuel and diesel V6 and V8 engines, and for the top of the line version, the Lamborghini V10.

This new model by Audi will be aimed directly at the competing Mercedes CLS, which became a best seller recently, due to the fact that Daimler-Chrysler is still the only one with this type of car on the market.

Therefore, not only Audi but also Jaguar and Volkswagen are striving to get a rival up and going as soon as possible. Jaguar’s version will be the upcoming XJ replacement and Volkswagen is developing a Passat-based coupe with four frameless doors as well.

The photos are showing: two computer images giving an artist’s impression of how the new A 7 could look like upon its release and two pictures of a prototype mule at Nürburgring.