No, it will almost certainly end in fiery doom...
Ok, so slightly more seriously no, I think that as it is essentially a re-dressed A4 they assume that the NCAP results for that apply to the A5. Audi presumably took the decision that they don't sell enough of them to warrant a separate NCAP test as it isn't going to affect sales, or more precisely not affect them to the extent that performing a full NCAP is worth it.