These latest prototypes are still draped from head to toe in swirly camouflage, which does an excellent job of hiding many of the car's styling details.
We know from earlier reports that the next-generation A4 will feature evolutionary styling. The first production vehicle to proudly bear the full stamp of Audi's new design language, as previewed by the Prologue, Prologue Avant and Prologue Allroad concepts, will be the next-generation A8.
While the S4 prototypes seen here aren't fitted with production-ready grilles, we can see that the car's headlights are shaped like kicked-over Ls, as the LED driving lights follow the units' edges.
Rumours indicate the next-generation S4 sedan and wagon will receive a slight power bump to between 250kW-260kW of power. The current S4 has 245kW.
Just as significantly, the next-gen A4 will use the latest version of the Volkswagen Group's MLB platform matrix for longitudinal engined vehicles. This should see most models in the range shed around 100 kilograms in weight, benefiting both fuel economy and performance.
Audi has already confirmed that the new A4 will debut this year, with many expecting the next-generation car to have its debut at the 2015 Frankfurt auto show that takes place in September. This makes an early 2016 launch down under likely.
It's not known at this stage when the faster S4 variants will debut.