We're only speculating, but perhaps the problem – if there really is a problem and this isn't Ghosn machinating – has to do with this tidbit taken from the IL story: "Ghosn approved the original GT-R only after being assured that it would make money for the company even at low volumes." We wouldn't be suprised if the shade under 6,000 sales in four years is quite a bit lower than the "low volumes" predicted in Nissan's original cost/benefit calculus.
At launch, the 480-horsepower GT-R MSRP was $69,850, or $71,900 if you wanted the Premium model. Peanuts are cheaper, which is probably why the GT-R has cost substantially more every single year: after its first year, the price jumped to $76,840 for the base model and $79,090 for the Premium; the next year brought a price bump to $80,790 or $83,040 for the Premium; the following year, the base model disappeared and the Premium rose by a premium of $1,020 to $84,060; in 2012 the price took another leap to $90,950; and for 2013, it was another gulp-worthy price boost to $96,820. Yes, the 2013 iteration has 55 more horsepower than the original model and a 2.7-second 0-to-60 time, and yes, you'd look a long time for a sub-$100K car to match its performance, but at that price, the GT-R is mixing with the kinds of sexy metal that can bring attributes to the table that the GT-R can't match.
But of course, along with not knowing if Ghosn will approve a followup to the current car, we don't know why he hasn't done it already – maybe he's changed his mind about that Infiniti GT-R after all, or maybe he hopes you'll be satisfied with the Juke-R. If this car is a "one-hit wonder," though, it was certainly a wonder, if perhaps not enough of a sales hit.