According to UK "Car" magazine, the upcoming Audi RS5 will be fitted with the excellent high-revving 4.2-litre V8 that powers the RS4 plus the addition of two small and highly responsive turbochargers that will take peak power up to 330kW (450hp). This should translate to a 0-100km/h time of 4.5 seconds and an electronically limited top speed of 250km/h.
Looks like the upcoming BMW M3 and the current Mercedes CLK63 AMG has a real fight on their hands.