Seems more than achievable to me. Jonny in his current state of tune will have roughly 280bhp/tonne, where as a R8 has 270bhp/tonne. Throw in the DSG changes over some dude that might be a bit slow on the stick, plus the fact that if the R8's are anything like the RS4, it probably won't be making the 414bhp it's stated to have anyway..
The R8 will always come past eventually at seriously high speed, but in a straight acceleration test i'd have my money on the Ed30..