ケイマンGT4は3.8Lツインターボ？

ケイマンGT4はフラット6の3.8Lツインターボで450馬力という記事が出てますね。

The upcoming Porsche Cayman GT4 will reportedly be offered with a flat-six 3.8 twin-turbo boxer engine rated at 450 PS.
Several spy shots have already confirmed Porsche is planning a new range-topper for the Cayman lineup that will probably receive the GT4 moniker. Now, CAR says the model is going to pack a flat-six 3.8-liter twin-turbo engine developing somewhere in the region of 450 PS (331 kW).
Aside from the 911 Turbo engine transplant, the hardcore Cayman will also come with a large rear wing, bigger vents and uprated brakes. Also expect a stiffer suspension arrangement, functional rear diffuser, unique alloy wheels and centrally-mounted dual exhaust pipes.
Set to come out next year, the Cayman GT4 will be allegedly followed by other derivatives as it is believed Porsche has decided to extend the model's lifespan.

色々なところで噂されるケイマンGT4のエンジン。
一体どんなエンジンが載るのでしょうか。。
フラット6？
4気筒？
NA？
ターボ？