The classic 911 continued to be produced until 1989 - more than 25 years after it first launched.
Probably the most significant event in the lifespan of the original 911 was the introduction of the 930. This name can be a bit confusing, but if it wasn't, we wouldn't be talking about Porsche. Porsche decided to give the turbocharged 911 a different type number than the rest of the lineup, but only for this generation. Therefore, from 1963 to 1989, all N/A 911 models are simply called 911, while all pre-1989 turbocharged models are 930 911s.
Then, when the 964 911 came out in 1989, the type number was applied to all 911 models. Therefore, N/A 911 models would be 964 911 Carreras and turbocharged models would be known as 964 911 Turbos. This slightly less confusing nomenclature was kept through the 993, 996, and 997 generations of the car, and will presumably be adopted for the current 991 generation once a Turbo model is introduced. The 930 was introduced in 1974 for the 1975 model year. Though it was the fastest production car in Germany at the time, its release came at the worst possible time.
The 911's biggest market by far has always been the US, but the gas crisis was in full swing by 1975, and sales of performance cars were slumping. Porsche therefore devised what they thought would be the replacement for the 911, the 928. This was a bigger GT car with a front-mounted and water-cooled V8, something Porsche felt would be better suited to the times. The car was not without its charm, and it was certainly easier to drive than the 911, but it never caught on, and didn't outsell the 911 for a single year of its 18-year production cycle.
What people really wanted was the 930, which was positioned at the top of the 911 model lineup for the whole time it was produced. It was originally conceived as a homologation car, but Porsche realized its value in the lineup and used it to plug the price gap between the standard 911 and the more expensive Italian exotics. Thus the Turbo was both good engineering and good business, earning it a spot in the 911 lineup in all subsequent generations. A race version of the 930 was built, known as the 935. It was built to meet FIA's Group 5 rules, and it was a huge success.
It won a total of 123 out of the 370 endurance races it was entered in, culminating in an overall victory at the 1979 24 Hours of Le Mans. So iconic was this racer that Porsche even offered the "slantnose" body style for road-going 930 models, by special order, or course. But by end of the Seventies, the 911's future was far from the secure. With the 928 being introduced in 1977, Porsche had initially planned to drop the model after 1981. Had certain forces inside the company not put forth the case that the 911 was the backbone of the entire company, then this might very well have happened.
But the 911 supporters won, and fresh money was put into development, starting with the Cabriolet. This convertible debuted in concept form at the 1981 Frankfurt Auto Show, and it was the first true convertible to be offered since the 356. Prior to this, the only choice for an open-top 911 was the Targa, a version of the hardtop with a removable roof section. This wasn't a true convertible, but Porsche had only built it because they had been afraid that the NHTSA would ban true, fully-open convertibles in the US, and they didn't want to sink any development money into anything that would be unavailable in the 911's biggest market.
These were a big success, and the 911 got a new, bigger engine for 1983. Porsche was once again committed to 911 development, and the biggest step in this development was yet to come. IT's difficult to say where the 959 really belongs in the story of the 911. Its production spanned the end of the original 911 and the beginning of the 964. Technologically speaking, it has more in common with the 964, but development started several years before the 964's introduction, and even its name suggests something that came before the 964. It doesn't really belong in any generation, but it is hugely important to the history of the 911.
It was the car which Porsche used to prove just how potent a car the 911 could be. In a way, it was a window into the future, as almost all of the features which had seemed wildly futuristic at the time would find their way onto regular 911 models within a decade or so. It also showed that Porsche had jumped back into the 911 with both feet, and it strongly hinted that the car would begin to make the migration from sports car to supercar.