Hmm... I think that you will have to except the fact that RS5 will be faster in 0-200km/h then R8 V8. Yes, that fact is IMO hard to except.
BTW, fastest R8 V8(manual) measured by German magazines reached 200km/h in 15.1s(tested by AB Sports Car Edition). Various other examples were between 15.8s-17.2s
Fastest R8 V10 was measured at 12.3s. At least it meant Audi factory claim which for R8 V8 is unfortunately not true.
Since M3 MDCT is as fast in straight line as R8 V8 we can assume that RS5 will be faster then both.
Here are a few more spy shots in Barcelona:
Source: Worldcarfans