By lowering the weight Audi will not have to develop all new motors. Simply some mild tweaking for the V8 and V10 likely around 25 horsepower each. Shedding weight is just as good as adding power and better really as it improves all performance aspects not just acceleration. Efficiency as well which is one of the reasons the VW group is investing in lightweight materials such as CFRP (carbon fiber reinforced plastic) and aluminum.
So much like the new SL from Mercedes the car will be familiar but more efficient, more powerful, and lighter. That's progress.