The dead giveaways that this is the RS version of the A7 are the big fender flares at each corner. The ones on this prototype appear to be unfinished and are just there to keep the tires covered. What is there looks fairly well integrated, though, so we wouldn't be surprised if Audi uses a more complete version of them on the production car. There's also the chance that Audi will simply widen the fenders instead of using flares, as the company did with the last RS7.
Another indication that this is the new RS7, and that it's close to production, is the distinct front fascia. This RS7 has much larger grilles on either side of the central one than those on the A7 and the S7 prototypes we've seen. Not only that, but they have a triangular shape not shared with the lesser models.
Around at the back, things look pretty much the same as the regular A7, but we suspect that's not the case for production. This is because the rear bumper is in fact the same as the regular model, but the stock exhaust openings have been chopped out to make room for the RS7's twin oval exhaust tips. We're certain Audi will have a more integrated and unique design for the production bumper.
Audi has been readying the Audi S7 for a while now, and this RS7 doesn't look far behind. We're expecting them both to be revealed sometime in 2019 in time for the 2020 model year. Some kind of turbocharged V8 seems like a safe bet for the RS7, especially if it's going to match the 605 horsepower of the previous model. The S7, on the other hand, may use either a turbo V8 or a turbo V6.