Yeah, that might be carrying the analogy out beyond the point where it stays relevant.
But to play along...
The fixed blade knife, maybe like the revolver, is now pretty much what it has been for a very long time. We've improved it, and some folks will tell you that their special combination of steels and handle materials, and shape and blade contour, and sheath, etc., makes the fixed-blade knife they're selling substantively different that anything before. And of course, that's 95% total crap.
With folding knives, maybe like autos, we've come up with some pretty nifty improvements. 17 different ways to lock the blade open, for example. Every one being, of course, better than any of the others. But when we took it to the next level (let's say automatic knives) we ended up with something that's more ... nifty ... than necessary, or even desirable for most people. I'd say that's going beyond the pinnacle of perfecting the concept and starting to head down the far side of the development curve.
So what's left for knives? Will we ever see the next great thing? Sure. When we have some kind of controlled cutting beam technology or energy blade or something similar to micro-light saber. And then we'll have what I alluded to before: "something truly world-changing comes along which either sweeps that technological accomplishment into a wildly new evolution, or sweeps them ... into the realm of the archaic."