Gun Control & RKBA

"The concept of market saturation does not appear to apply to weapons sales regardless of caliber, rate of fire, barrel length, portability, concealment factor, or prominence"

Of course market saturation applies. But you are looking at the wrong criteria. And long guns already have greater market saturation than handguns; the difference in misuse boils down to the fact that you can't stick a 26"+ rifle in your waistband under a T-shirt. Long-gun misuse has actually declined considerably today compared to the 1970s.

It's not mass murders that drive rifle sales, though. It's the fact that every time there is a mass murder, journalists and prohibitionists demand that future rifle sales to the lawful and nonviolent be constrained. So if you have just come of age to own guns or have just never gotten around to buying that rifle you wanted, the politicians/media push people to hedge against the possibility of bans. Josh Sugarmann and Michael Bloomberg have together sold more rifles than any other two people in U.S. history, IMO.

As to the criteria you list, caliber is already constrained by law and practicality; anything .51 caliber or higher is banned unless exempted for "sporting purposes" (that's how .729-caliber 12-gauge shotguns are legal), and anything less than about .20 caliber is small to be practical under Federal rifling rules, so civilian caliber has been stuck between .22 and .50 for a century and will probably stay there.

Civilian rate of fire has been limited to one shot per trigger pull for nearly a century and will likely stay there.

Civilian barrel length for rifles is 16"-24", constrained on the low end by Federal law and on the high end by practicality.

Portability/concealment are inherent to the type of weapon, not to technology. Most handguns are concealable; rifles are not. Rifles and shotguns are still required to be at least 26" long with 16" barrels minimum; you might be able to make a rifle lighter with future materials, but you can't make a rifle disappear into a waistband or pocket.

I'm not sure what you mean by "prominence". The AR platform is the most common civilian rifle in U.S. homes, but does that make it "prominent"? If so, does that mean it should be banned, or that it should become the national standard? Not following you here.