Pragmatically, the Savage was designed in the '60-70s with commonly available '60s sheet metal and investment casting technology to price/performance compete at the lower end of the motorcycle market.
It originally sold dirt cheap and competed with 250-350 Honda, Yamaha and Kawasaki twins for that "beginners" market slot. It was designed to be easier/cheaper to build than a 250-350 twin yet giving equivalent performance. The relatively huge displacement was cheap to do and it was necessary to make up the performance difference. There are no bells and whistles on the bike, it was 1960's minimal tech all the way (but still meeting all legal requirements for safety and lights, etc).
Now, in 2009 Suzuki sees a bike that has all its tooling paid for 5x over and they don't need to mess with it at all since (aside from the tranny upgrade model change and the cam chain tensioner system that got a lick and a promise just a few years ago) everything works good and is fairly durable. As long as Suzuki can lean out the carburetor to meet EPA requirements, they will keep building a single limited production run at the start of the year and selling it out at a slight premium that goes into their dealer's pockets.
(when fuel injection becomes necessary the ongoing saga of the Savage may undergo a serious review as you are dealing with Suzuki/Kawasaki as a merged entity now and there are pressures to integrate the combined offerings to cut out internally competing replications)
The Savage sells out each year because when a buyer looks at it he sees solid metal and visually appealing lines. Visually, the buyer sees Harley solid metal style '60s technology and he likes it. The buyer then looks at other bikes in the price range, sees a lot of plastic and fold metal kickstands and such and he then picks the Savage (and it sells out early every spring).
It sells out early each spring at a premium price (extra markup dollars going into the dealer's pocket - they like that). It has a cult following of sorts. It requires no redesign and is now competing in both low and mid-range market slots. Why would you kill it?
Why indeed? There are some reasons ...
For example, Kawasaki has a 650 single dirt bike with a better motor, but it doesn't look as good as the Savage. The retro look sells -- so as long as the slot gets filled with something that sells out each spring.
What is sad is there are several alternatives to the market slot that could be built out of existing 450cc to 650cc dirt bike models in both the Suzuki and Kawasaki lines that could share a production line for cost effectiveness.
Sure, the old Savage production line is paid for, but cost of say "moving it to another facility" could prompt a model review. Costs of meeting some new EPA goal that pushes leaning out the carburetor past the Savage's admittedly broad reliability limits could also play in causing a model review.
What threatens the Savage most is China. Savages sell at a fairly high price compared to current Chinese 250cc bikes, but the Chinese bikes don't perform all that well (they are aimed at excellent gas mileage).
You let the Chinese screw up and photo-copy a high output 90 degree SV650 motor and put it in a low seat height frame to suit the oriental leg length and suddenly the Savage has some competition it can't overcome at a similar price point.
Count your blessings that China does not believe in performance per se, but only believes in excellent gas mileage as defining the motorcycle. When that mind set changes the motorcycle world will see serious competition for the low end of the market way beyond what it sees today.
http://www.megapowersports.com/motorcycle.html