Audi has released a teaser sketch of its upcoming four-door coupe that’s due to hit showrooms by September of 2009. Before that, we should see a near-production ready concept version, most likely at the 2008 New York Auto Show.

According to the Audi source that leaked the sketch, the A7 will feature a range of V-6 and V-8 powerplants, with high-performance V-10 units reserved for the S and RS sports models. Pricing will start below that of the A8 flagship but a new convertible version could turn out to be the most expensive Audi on sale.

The A7 will have some serious competition by the time it arrives. Sister company Volkswagen is preparing its own low-priced four-door coupe and BMW is also prepping a new flagship model based on the Concept CS. Then, of course, there’s the Aston Martin Rapide and Porsche Panamera as well as segment starter, the Mercedes-Benz CLS, which is due for a facelift next year ahead of an all new model in 2011.