In the United States, we've never been able to buy Audi's hardcore wagon models like the RS4 and RS6. After an inside source told us this may change with the arrival of the A6 and RS6 Avants in the US, Audi went on Twitter to tease the return of Avant models. Nothing has been officially confirmed as of yet but it seems like a good bet that the US may finally be treated to an Audi wagon with over 600 horsepower on tap.

We've seen Audi testing prototypes of the RS7, which will almost certainly continue to be sold in the US, but now we have our first look at the upcoming RS6.

Although we've previously spotted the S6 Avant testing on the Nurburgring, this is our first good look at the hardcore RS6. This RS6 prototype is more camouflaged than the S6 but we can still pick out a few distinguishing features including an angular front grille, large twin oval exhaust pipes, wide fenders, and massive brakes behind those large black wheels.

The engine powering this new RS6 still remains a mystery. Some rumors indicate it could borrow the hybrid drivetrain from the Porsche Panamera Turbo S E-Hybrid, producing close to 700 hp. Other rumors say it will simply use a tuned version of the Audi's 4.0-liter twin-turbo V8 producing around 600 to 650 hp.

Either way, if the RS6 does end up coming to the US, it will be among the most powerful wagon models on the market. Only the Mercedes E63 S Wagon will even come close with 603 hp. Based on what we've seen so far, the RS6 will only be offered as a wagon, though a sedan model could be planned as well. We expect the RS6 to be revealed in September during the 2019 Frankfurt Motor Show.