I've been thinking for a couple of months now that prompt engineering, and therefore CoT, is going to become the "secret sauce" companies want to hold onto.

If anything that is where the day to day pragmatic engineering gets done. Like with early chemistry, we didn't need to precisely understand chemical theory to produce mass industrial processes by making a good enough working model, some statistical parameters, and good ole practical experience. People figured out steel making and black powder with alchemy.

The only debate now is whether the prompt engineering models are currently closer to alchemy or modern chemistry? I'd say we're at advanced alchemy with some hints of rudimentary chemistry.

Also, unrelated but with CERN turning lead into gold, doesn't that mean the alchemists were correct, just fundamentally unprepared for the scale of the task? ;)

The thing with alchemy was not that their hypotheses were wrong (they eventually created chemistry), but that their method of secret esoteric mysticism over open inquiry was wrong.

Newton is the great example of this: he led a dual life, where in one he did science openly to a community to scrutinize, in the other he did secret alchemy in search of the philosopher's stone. History has empirically shown us which of his lives actually led to the discovery and accumulation of knowledge, and which did not.