At first glance, the car pictured here looks like an LFA with the Nürburgring Package and some camouflage on the front and rear fenders. If you look closely, you can see that the fenders are significantly wider than on the standard LFA. Based on the license plate, this appears to be the same car with two different sets of wheels. Lexus may simply be swapping out worn tires, or they may be testing different wheel and tire combinations to fit the wider wheel wells.
Anything beyond this is just speculation. There have been rumors of a new flagship Lexus sports car that sits atop the LC 500 and LC 500h. We saw the Toyota GR Super Sport Concept back in January, though that car looks nothing like what we see here. As much as we would love that sweet Yamaha co-developed V10 to carry over, we're not holding our breath. Some sort of hybrid powertrain is almost a certainty. Maybe Lexus and Toyota could pull some tech from its Le Mans-winning TS050 Hybrid race car.