There aren't many changes to the exterior of the car, which does hurt the argument that this could be an R8 GT. The front fascia and flanks appear to be identical to the normal R8 in fact. The old R8 GT at least featured a couple extra canards at the front for better aerodynamics.
At the back, the car seems to have the same wing as the R8 Plus, which is similar in shape and size as the old R8 GT. The rear grilles also look different. The actual openings appear larger and closer to the rear wing, and the mesh pattern looks as though it might extend behind the rear license plate. The diffuser is also new, and it looks a bit wider. It also now encompasses oval exhaust tips. Oval tips have frequently been a cue on RS Audis, so perhaps this R8 could carry an RS badge. Our spy photographer tells us the exhaust was very loud, too.
Since this prototype doesn't look vastly different from the current R8, we're expecting that it won't be a terribly long wait to see the final product. Perhaps one to two years. We hope.