A statement from Nissan reads:
"Nissan North America is consolidating its motorsports presence to showcase the Nissan GT-R in the Pirelli World Challenge GT category for the 2016 season.
"Nissan will continue to support grassroots motorsports efforts in SCCA, NASA and other organizations, as well as continue to retail performance and motorsports components through its Nissan Motorsports Competition Parts arm.
"Nissan wishes to thank Doran Racing for four excellent seasons of competitive racing with the 370Z and also IMSA for their support of road racing in North America."
Nissan, in partnership with Always Evolving Racing and AIM Autosport, is expected to have at least two and potentially three GT-Rs in World Challenge next season. Heitkotter and James Davison were the two drivers there this season.
It is unclear whether any GT-Rs would be able to race in the Rolex 24 at Daytona, as had been rumored earlier this winter.
The manufacturer, however, will be present in the Prototype class, at least in the opening two WeatherTech Championship races of the season, with SMP Racing's Nissan-powered BR01 and the DragonSpeed Oreca 05 Nissan, which are slated to compete at Daytona and Sebring, respectively.