The recently-unveiled Toyota GR Supra Racing Concept will be making its eventual racing game debut in Gran Turismo Sport.
Derived from the Toyota FT-1 concept car (which, in turn, gave rise to a motorsports-inspired Vision Gran Turismo variant), the Toyota GR Supra Racing Concept will be introduced to Gran Turismo Sport sometime in April 2018.
More specific details on when the Toyota GR Supra will be introduced to Gran Turismo Sport likely won't be known until the update it will be contained in is officially released.
It's also worth highlighting the "only Gran Turismo players will be able to experience [the car's] performance" quote from Polyphony Digital's official statement. Considering the choice of words, it's highly likely the Toyota GR Supra will remain a Gran Turismo exclusive vehicle for at least a limited time.
Unveiled in full at the 2018 Geneva Motor Show, the Toyota GR Supra Racing Concept is the latest in a long line of sports car concept cars produced by Toyota. More importantly, the GR Supra design study also previews the aesthetic of a future Toyota Supra production car – with the decision to showcase the car initially as a racing vehicle heavily suggesting a motorsports version of the all-new Toyota Supra is in the pipelines.