Posted this twice. Here and on the other thread.
I think of this car as a Japanese Cadillac CTS-V. Sure it will be fast, sure it will handle well, sure it might have a few luxury appointments, sure it might have some of the latest tech, aside from all that though, I think it will be on the same level as the CTS-V and maybe with similar pricing. The last generation CTS-V was already making nearly the same horsepower and way more torque, had some nice luxury aspects, was priced $30-$40k less than an M5, and did that car sell like hotcakes? Nope.
I think the biggest single factor in a possible future 4-Door GTR-ish car will be the market price that Infiniti demands for it. If they demand over $100k for it, then who would be willing to pay that for an Infiniti. Kind of the same thing happened with the Lexus LFA. $400k for an incredible sports car, but your still only driving a Lexus. Some people care about that, others don't.
Me personally, I wouldn't be caught dead in an Infiniti, even if it came with performance that equaled or bettered the F10 M5, but came with 3/4's the luxury, utility, comfort, convenience, and technology that the F10 M5 has. Plus I don't care for AWD on a Sports Sedan. If I wanted that, I'd go buy an Audi. If a future 4-Door AWD GTR is in fact made, I have a feeling that like the current 2-Door GTR it will have no feeling. That is to say it will still feel like driving a robot, there will not be enough sensation, feedback, and puristic driving pleasure as I get with my F10 M5. For someone who only cares about speed, sure go buy the new Infiniti GTR, have at it I say.
I do like the fact that JDM companies are trying to break into new markets though. It's just that a lot of the little things that the Germans have been perfecting for year and years will not be present in any high performance JDM Sports Sedan. In the end, I love the fact that Nissan and Infiniti are playing with this idea. It only inspires competition and from a consumers point of view competition is a very good thing.