My contention with the axial-flow separator, regardless of what color it is, is that most of them don't feed very well or very evenly, and so to overcome that little problem, pump up the power until it'll digest a 2x4. I ran cylinder/walker machines for a very long time, and learned early on that a combine only functions as well at it's fed. I think that's why we now read of chaffer/rotor losses like we used to read about chaffer/walker losses. I know that if I could achieve even feeding, I could increase machine capacity and could pretty much stop chaffer and walker loss within machine limits---in other words, keep it FULL, but not overloaded.
Today, because of the feeding problem, the capacity limits of the 30-inch axial-flow rotor have about been reached, now they are just throwing more and more horsepower at them so they can call the machine a Class 9 by the addition of more horsepower, with no other changes in the machine. To build more capacity will take a larger rotor and even more horsepower.
No doubt rotary is here to stay, and old fossils like me had our day. But, I live in one of the better corn-growing counties in Iowa, and the majority of the harvest is still harvested with old 9XXX Maximizers. Oh, there's a handful of newer IH's around, and some STS's, but one local still runs a 7700, one a 4400, and there's a couple of very old 14 Series Axial-Flows. A couple of R-62's that are very impressive, that's a concept with a lot more potential left in it. Still, the old cylinder/walker machines do pretty well, and the elevators don't pay any more per bushel of grain for it being harvested with a rotary, as the advertising of that "other" company implied that it would in years past.