Are future improvements in Amp/PreAmps slowing to a crawl?

I could tell you what it sounds like. It sounds like no amplifier is in use.
As far as performance - It's more like a 3D sound projector.
The only thing you hear is the original venue fully "displayed" as an acoustic image. Turning the volume up and down acts as a zoom control that changes the distance or your proximity to the performance.

Aside from that being a non-answer...
Why exactly would a volume knob manipulate the spacial cues in a recording? 

bad tracking with channel to channel variation would harm spatial cues

Quite right, Randy. Roger there is basically reengineering the statement that an amp should behave like a straight wire with gain and there's no shortage of failings in that belief, chief among them being that few if any speakers present a purely benign resistive load. The problem with his interpretation of what a volume knob should do is found in the obvious fact that a flute played softly doesn't sound as if it's further away. It sounds like where it's at regardless of how loud or quietly it's played. It's ideas and talk like that which make me implacably skeptical of his claims of perfection.