From what we can tell from this test mule, Audi has kept the overall styling of the A3 Sedan very similar to the 2011 concept car. The long-lensed shots don't give us too much detail of the car's body or any interior shots, but we do see that the concept's roofline and side window shape carries over almost identically. As expected, the massive carbon fiber and aluminum wheels have been replaced with more appropriately sized wheels, and the door mirrors are befitting a production car. The concept had a four-passenger seating layout, but we would be surprised if this configuration makes it to production.
No definitive word on what will power the next A3, but don't hold your breath for the same five-cylinder used on the A3 Sedan Concept. With a stated 408 horsepower and 369 pound-feet of torque, this engine's output seems rather high even for a next-gen RS3.