US mag Motor Trend suggests both models will use an enlarged version of the 86/BRZ architecture, with reinforcements to permit the use of heavier and torquier hybrid drivetrains.
This report follows confirmation of an expanded Toyota/BMW partnership in January, which will now include an engine-sharing program, green technology development, and a joint sports car project.
The FT-HS hybrid concept from 2007 was Toyota’s first hint of a future Supra replacement, and the now joint project is reportedly being headed by 86/BRZ chief engineer Tetsuya Tada.
Reports last year suggested that the next Z4 would be lighter and more performance-focused to better challenge Porsche’s Boxster, and Tada-san's success with the 86/BRZ suggests he could deliver such a car.
The report adds that a 2.5 litre turbocharged four-cylinder hybrid drivetrain is likely for the Supra-replacement, which could produce more than 300kW.
BMW on the other hand will reportedly use an Activehybrid six-cylinder drivetrain to produce similar power in a potential Z4 range-topper.
While the next Z4 is due to arrive sometime in 2015, the Supra replacement is believed to be further away, due possibly in 2017.
A concept version of the new Toyota could appear as soon as November’s Tokyo Motor Show however, enabling the Japanese brand to ride the wave of the 86’s success.