Posted by Jalopnik, the rendering was supposedly based on the descriptions of people who have actually seen the racer. They described a car with a very long nose, and a rear that was potentially narrower than the front. From those details the pictures of a reverse Deltawing is almost conceivable. Judging by the original teaser image, this description actually sounds somewhat plausible too. The draping of the sheet in that photo could suggest some empty space at the back.
According to this rumor, underneath that long snout could be an even bigger revelation – the engine. These days putting the powerplant ahead of the driver in a top-class endurance racer – even if it's behind the front axle for a mid-engine layout – is almost unheard of. Nissan trying it would certainly fall under a different way of winning. Though, such a thing was done by Panoz in the 2000s.
Nissan is clear about keeping the racecar and road version at least somewhat related, especially technologically. Jalopnik speculates that the engine could be a gasoline-fueled twin-turbocharged V6 powering the rear wheels and a hybrid spinning the front and rear with a total system output of 1,000 horsepower or more. That figure is right on the money for modern LMP1 cars since the 2014-championship winning Toyota TS040 packs about 986 hp total.
In the past few years, Nissan has failed to finish Le Mans with both the Deltawing that it sponsored and the ZEOD RC project. If these rumors prove true, then even getting the GT-R LM to see the checkered flag could be quite an accomplishment no matter where it finishes. Rumor has it that Nissan might show at least a glimpse of the vehicle during the company's Super Bowl ad this year.