The RS4 is only a year old, but Audi is already working on the next car to wear the RS badge. Our spy photographers have recent caught a prototype RS6 saloon being tested on the Nurburgring in Germany, heavily disguised in camouflage paintwork to break up the cars’ outline, and it could be on the market next year. This new super saloon will use Audi’s version of the Lamborghini V10 found in the Gallardo. Audi’s S8 and S6 models already feature this engine, which at 5.2-litres is 200cc bigger than the Lambo unit, and has direct injection. The RS6, however, will need to better the S6’s 429bhp and 398lb ft, and Audi engineers are rumoured to be working on a twin-turbocharged version of the engine that could increase power to over 500bhp, and could also feature in the range-topping R8 supercar. This would be necessary for the car to compete with the 500bhp BMW M5. We’re not likely to see the RS6 until the middle of next year at the earliest. As a rule of thumb, Audi normally only ever has one RS-badged model in its range at any given moment, so this one won’t be available until the RS4 ends production. That’s likely to happen in Spring of next year when the all-new A4, to be unveiled at the Frankfurt motor show in September, goes into production.