The A7 body is actually based on the A6, so the conversion is rather simple. The super-powered four-door coupe would be powered by the same 4.0-liter twin-turbo V8 that already powers the existing S7. But output will likely be 560 PS (552 hp), just like the new RS6.
A fresh report from Autocar magazine suggests that the RS7 will actually debut sooner than we thought, at the 2013 Detroit Auto Show, which begins in mid-January. This is clear indication that the model is indeed coming to the US market as a 2014 model year, ready to fight the CLS 63 AMG and M6 Gran Coupe.