It has the full-width taillight design we see on every 992. It still looks good here along with the traditional GT3 center-exit dual exhaust. We heard awhile back that the GT3 will definitely retain a naturally aspirated engine, and not transition to a boosted flat six like the rest of the 911 lineup. The high-revving 4.0-liter flat six is almost a sure carryover for this next generation car then, too.
On this particular tester, it looks like there's still a lot that isn't final. The vertical mounts and decklid both look far from production-ready. That third rear brake light looks both weird and ugly, but don't expect Porsche to integrate anything that weird when it debuts. Maybe the large cladding on the wing mounts are blocking an active aero system? Or maybe it's manually adjustable? All we have are guesses for now.
Up front, the bumper is all covered up. If Porsche makes any major changes, they'll be seen here and with the rear fascia design, too. This is a 911, after all; the shape does not change. We've seen the normal 992 Carrera plenty of times at this point — the official debut is almost ceremonial. There will probably be a longer wait time for the GT3 version of the updated 911, though. Porsche normally staggers releases of its higher-performance variants of a new 911 over a few years, with the highest performing members rolling out last.