I think it is safe to assume that with the new GT-R Nissan will be going with a twin turbo VQ-series V6 in Japan, and a NA V8 in the US. Why? Simply because Nissan assumes that Americans prefer high-displacement V8s instead of turbo engines. Emissions also might have something to do with that. Is it fair to the GT-R legend? Ofcourse not. But I don't think Nissan/Renault care about GT-R heritage anymore, as evidenced by their removal of the round tailights and inline-6 motors from regular Skyline models. They're just out to make money now.
What I wish for, is a new RB-based but totally redesigned from the ground up Nissan inline-6 motor and a bulky R34 type Godzilla body. An evolution of the current GT-R you might say instead of a revolution. This way it will still stay true to the heritage of all GT-R's: inline-6 power, muscle-car body, and round tailights.
That will probably remain just a wish however, as Nissan does not want to spend money to design a new GT-R exclusive inline-6 motor right now.