How Audi will get around Porsche's jealous protection of the Boxster/Cayman niche is yet unknown, but presumably some element of cooperation has been found since Porsche's takeover of Audi parent company Volkswagen. Keeping the products sufficiently distinct that they tap into two different markets is also part of the plan, according to AutoExpress. With the raging success of the R8, it's hard to fault Audi for trying.
The R4 itself is expected to be powered by a 335hp (250kW) 2.5L turbo and supercharged five-cylinder engine (also expected for the TT-RS) in the range topper, while the entry model will likely get a 2.0L turbo four-cylinder, lending some weight to the assertions that Porsche may offer a Boxster/Cayman with a similar engine configuration. A six-speed manual or a seven-speed dual-clutch unit are expected to play the leading roles in the transmission department.
Jaguar has been talking about a new E-Type for several years now, and Audi will be ready when it finally does come: the R6 is thought to be intended as a direct rival. Details on this car are yet unknown, but expect it to strike a middle ground between the R8 and R4. That would place output near the 380hp (283kW) mark, with the car's size roughly that of a Porsche 911.
The much-lauded V12 TDI R8 diesel concept may be finally coming to production as well, in the guise of an R10 (not to be confused with the Le Mans racer). The concept car's 6.0L, 500hp and 738lbft (1,000Nm) of torque V12 diesel was all the rage at the dawn of 2007, but since then it has been consistently denied as a real-world production likelihood - much like the R4.
Denying the existence of future models even in the face of photographic evidence is standard procedure for most carmakers, however, so keep an eye out of this wide range of Audi R vehicles to hit the streets starting in 2011 with the R4.