A while ago the question got asked "what will be the last naturally aspirated performance car?" It's an interesting question, and it's bizarre to think future enthusiast might not get to experience a new non-turbo performance car. If you look at what's available today it's surprising to see just how few natural cars there are. Here's a rundown of what's left, and who I think will last.
Mazda MX5 Miata - There's a rumor floating around that we'll see a turbocharged Mazdaspeed Miata in the near future. For the foreseeable future though, a natural engine powers the base model.
Honda Civic Si - Perhaps the last sports compact car to not feature a turbocharger (I'm not counting the weakling CR-Z as a performance car). Strict emission requirements killed the old Type Rs so it seems likely they will kill the Si too. On the bright side Honda has finally given us a new turboed Type-R - turbo hot hatch>no hot hatch.
Scion/Subaru FR-S/BRZ - The Toyoburu's don't have any turbochargers yet, everybody has been expecting a high performance version but it still hasn't happened. So, even after all these years, the jury is still out on a turbo 'Buru, what about the base? Latest rumors say these cars might be a one generation wonder :(
Hyundai Genesis - It's hard to say what will happen to the Gen coupe going forward. Many think it will get Hyundai's V8, so maybe the little Korean coupe will be more pony car than sports car. If that's the case we might see natural V6s and V8s into the coming years.
Nissan Z - The current 370Z has been around for a while, and it's VQ V6 even longer. Nobody's sure about how or when the new Z will arrive. Engine speculation has gone from turbo four to downsized turbo six to holdover NA six. Basically it's anybody's guess as to if the Z will be turboed or not.
As with manual transmissions and V8 engines American muscle cars are a stronghold of tradition. That's not to say things wont ever change, for indeed they already have -all three have had supercharged versions of their pony cars (not to mention Ford's Ecoboost, or the turbocharged muscle cars of the 1980s). For now the lower end V8s seem safe, but it could only be a matter of time before the boosted engines creep in.
Dodge Charger/Chrysler 300
Chevrolet SS/Holden HSV
It seems Lexus missed the memo that sports sedans have almost gone entirely turbo/supercharged. Audi and Mercedes have some older versions of their performance cars that will likely be updated with turbocharged engines in the near future, leaving only Lexus with a non-turbo sports sedan. Somewhat ironic given Toyota's glorious turbocharged past.
Mercedes C63 AMG (replaced with a turbo)
Lexus RC F
Lexus GS F (coming soon)
Mercedes SLK55 AMG
Porsche Cayman/Boxster - With the 911 going all turbo it seems likely the Cayman and Boxster will go all turbo in the near future.
Porsche 911 - The 911 is expected to go all turbo soon, a possible exception is the GT3.
These two American icons will probably be among the last cars standing with out a blower/turbine. The top end Corvettes have gone supercharged but the base models seem to have a comfortable formula going. The future of the Viper is uncertain, knowing Chrysler they'll find a way to keep the V10 alive, but they do have a pretty impressive supercharged V8...
Audi R8 - Audi recently announced the next gen R8 will keep the NA V10, personally I'm skeptical it will stay around long, because they also have a new turbo V8.
Maserati Gran Turismo - Will probably soon get the Quattroporte's turbo V8, or just turbo V6s.
Aston Martin is supposed to get their V8s from Mercedes going forward. These engines will likely be based on the AMG GT's V8. That's not a bad thing given that particular V8 seems pretty impressive, yet it will be the end of English NA V8s. The twelve cylinder Astons are another matter. Aston recently updated their venerable V12 so it may have a few years left in it, but it's probably a matter of time before it goes away or gets replaced by a Mercedes unit.
Aston Martin Vantage
Aston Martin DB9
Aston Martin Vanquish
Both Ferrari and Lamborghini seem likely to keep their non-forced induction ten and twelve cylinder engines as long as environmental regulations will let them. Both companies seem to be toying with saddling their V12s up to a hybrid system (ex. LaFerrari, Asterion) so perhaps NA V12s can live on a while longer.
Ferrari 458 (soon to be replaced)
Porsche 918 - All that fuss over the electric motors it's easy to overlook the fact that Porsche squeezes over 600hp out of a 4.8 NA V8.
In case you didn't notice this list is incredibly small. We've got: Miata, Civic Si, FR-S/BRZ, Genesis Coupe, 370Z, Camaro, Mustang, Challenger, Charger, 300, SS, C63AMG, RS5, RC F, GS F, Cayman/Boxster, 911 GT3, Corvette, Viper, R8, Gran Turismo, Vantage, Vanquish, DB9, Huracan, FF, F12, Aventador, 918, and LaFerrari.
My predictions say the American V8 (pony cars, Corvette, LX cars, and we'll lump the Viper in here too) will last the longest. The high end V10/V12s from Ferrari and Lamborghini will probably last a while longer too supplemented by hybrids. On a similar note, I think Toyota, as a company, might be the last to fully adopt turbos. Opting instead for hybrids.