"Mainstream" or "Legacy" dirt bike manufacturers eliminated the low priced dual sport. Frames went from flexible and flimsy to exotic and expensive, even for dual sport bikes. The demise of the 2-stroke engine contributed to the problem (emissions), but now, we have two types of dirt bikes to choose from: underpowered Chinese 4stroke clones and expensive non-Chinese exotics.
This just plain sucks. Why don't we have a 25-30hp 4 stroke dual sport from either Chinese or the rest in a stiff steel frame with modest components for $$3500-4000?
Chinese manufacturers are about to, or already have begun to fulfill this niche, but you can't buy them, and they are oriented towards exotic. You see ~300cc 4 stroke motocross clones from China are out there, but the seats are hard, and ergonomics are oriented to 100% standup operation (true MX), and there aren't any distributors in the US for these bikes.
If you look for old dual sport bikes to rebuild, the "WANTED, old motorcycles rebuilders" are all you see. Years ago, I found a 70's TS250 in excellent shape, fixed it up and sold it to a collector, and now I regret selling it. I assumed that the market would crank out bikes like that. Nope.
Unless something changes, I think the low end market will still be dominated by Chinese bikes. You will be faced with a $10,000 price tag or pick up a Chinese bike and modify it. WTF?
Most dual sport riders do NOT ride extreme off road. Most riders are not lean, strong, young, extreme riders pretending to be MX winners. Most just want to have some fun off road on a bike that doesn't flex like a bamboo pole, and has enough power to easily make 70mph with a headwind or a modest hill on the road. But that bike isn't available unless you spend $10,000.
I wonder what the next 5-10 years has for us. My guess is that Chinese bikes will not change. MAYBE we will see moderate performance dual sport bikes that have modestly upgraded frame stiffness, adequate shocks, and higher horsepower/torque specs. Maybe not.