The 918 didn't sell out immediately. Saying it did is revisionist history. A very close relative is basically a friend of the factory and turned down multiple opportunities to purchase one under msrp. I won't name the dealer but he was called multiple times to see if he would be interested in their slot. They weren't sitting on lots but they still had to sell the car before they could build it.
http://www.caranddriver.com/reviews/2015-porsche-918-spyder-first-drive-review
"Before you start complaining that the 918 is too expensive, consider this: At a starting price of $847,975, it actually represents a saving of about a half-million bucks compared with its Ferrari and McLaren contemporaries. Those two, though, at 950 and 907 horsepower and each about 3300 pounds, have the potential to best even the 918’s astounding Nürburgring record. Those two are also sold out—the Ferrari before the public even knew anything about it.
Porsche, on the other hand, still has about half its 918-unit 918 production run available."
https://www.digitaltrends.com/cars/low-porsche-918-sales-might-spawn-a-four-door-version/
"The Porsche 918 hybrid supercar took more brainpower and money to build than Porsche had originally fathomed. Luckily for Porsche, though, the 918 is selling like hotcakes. Oh I’m sorry. I was thinking of the Ferrari LaFerrari. No, the 918 isn’t selling well at all."
https://www.autocar.co.uk/car-news/new-cars/porsche-confirms-918-spyder-sold-out
https://www.digitaltrends.com/cars/...lls-out-and-porsche-contemplates-a-successor/
March 2011-November 2014 is not how I'd define sold out immediately.
There are lots of cars that are low volume and don't continually evolve. BMW 1M for example. 1 year- 700 cars- 55k msrp. That's a production car and no one would argue it isnt. 918 improved on the carrera gt there will be something that improves upon it.