It definitely sounds supercharged to me. Its kinda rough and not melodious actually. So its either 4.4 TTV8 or TT V10 from the M5 or the new TT V12 (from the new 7 series).
I do not believe they would go for the V12 due to emmisons, TT V10 is a nonsence since I hear the next gen M5 is getting a new TT V8 (
) so it looks like its gonna be the current 4.4 TT V8 tuned to 500hp..