I can see why a GT 370 would be the test development car. Since Nissan usually release the Nismo a couple of years in. I still feel the Nismo should be the development car.
The Q60 engine did have a 300 hp version. That could be an option for a more toned down lighter Z. But the twin turbo VR30DDTT would always be the better option. Just dont expect anything above 21 Miles per gallon if theres no hybrid tech mated to it. At least youll get 360 ft/lbs of Torque. Which 90 ft/lbs more than the current Nismo at 270 ft/lbs. Obviously you cant compare to the 440 ft/lbs of Torque from the average remapped single turbo v6 diesel
In regards to styling, they have a lot of time to do something sleek and more in tune with the 350Z. I think any styling should be headed that way with a touch of Nismo. Since more people were fans of the 350Z. Im sure the designers would want it to have cues from the new Juke. The only thing id take exterior wise are the slim LED headlights and more potent Rear tail LED lights
I guess 2020 is a no go. Tokyo Motorshow didnt happen. So might be waiting 2 years before you hear a yes or a no