That timing should see the R4 lining up alongside the larger, second-generation R8 supercar, with which it will also share styling themes, inspired by the E-tron Spyder concept.
Read more on the Audi R4's VW and Porsche sister roadsters
Until Stadler made the key decision, the sticking point for the R4 programme had been its proposed construction. Plans initially called for a relatively simple and cost-effective steel unitary body arrangement with component sets taken from the Volkswagen Golf.
Engineers also considered basing it around a more complex aluminium spaceframe design; that would have been expensive, but would have provided added engineering integrity. However, the decision to bring Porsche into the project in early 2010 has seen a further evolution in the plan.
Insiders now suggest the production version of the R4 will share major elements of its front-end structure with the third-generation Boxster – itself closely related to the 911. The R4’s rear structure, however, will be “radically different”, according to one Audi source.
Read Autocar's VW BlueSport concept review
Engineering efforts are concentrating initially on two petrol engines, a similar strategy to that used on the R8. As with all models based on the Group’s new MMB platform, they will be mounted transversely behind the cabin and deliver power to the rear wheels, a layout that allows significant parts sharing with front-drive engine and gearbox modules.
Although a launch model has yet to be finalised, Audi sources suggest the car will run a modified version of today’s 2.0-litre four-cylinder turbocharged engine, featuring a new variable cam and valve lift control system that was recently unveiled at the Vienna engine symposium.
This new unit, likely to get its first airing on the third-gen A3 in early 2012, is said to kick out 230bhp in standard form. A more heavily tuned 280bhp version is planned for the new S3 and due out in late 2013.
Read more on Audi's all-new A3
The attention-stealer, however, is set to be a range-topping 350bhp version developed by Quattro GmbH and powered by the same turbocharged 2.5-litre five-cylinder powerplant from the RS3 and TT RS. With 350bhp — 35bhp more than today’s most potent Boxster — it promises heady performance with 0-62mph in less than 5.0sec and a top speed of around 175mph.
The five-pot variant is likely to follow a couple of years after the R4’s initial launch; an on-sale date of around 2015 looks likely.
A bigger surprise is the very strong possibility of a diesel powerplant in the line-up, as part of a push to link Audi’s Le Mans 24 Hours successes in diesel-powered endurance racers with its road cars.
A strong candidate is a yet-to-be-seen twin-turbocharged 2.0-litre four-cylinder oil-burner, set to be aired in next year’s A3 and likely to make at least 200bhp and 295lb ft.
Full story - Audi's 500bhp A1 quattro
As part of the modular engineering strategy behind the MMB mid-engined sports car platform, Audi plans two gearbox options: a standard six-speed manual and a seven-speed S-tronic dual-clutch unit.
Also under consideration is a new, electronically-operated differential with torque vectoring to boost traction and make cornering more neutral.
A lesser priority, according to senior Ingolstadt officials, is an electric version based on the E-tron Spyder revealed at last year’s Detroit motor show.
Volkswagen Group’s modular plug-in electric architecture will provide the motive power, possibly in conjunction with four-wheel drive.