You are missing the economic component.. it isn't just how small can a transistor be.. it was really about how many transistors can you get for your money. So even when we reach terminal density, we probably haven't reached terminal economics.
I didn't say we have currently reached a limit. I am saying that there obvious is a limit (at some point). So, scaling cannot go forever. This is a counterpoint to the dubious analogy with deep learning.
The limits are engineering, not physics. Atoms need not be a barrier for a long time if you can go fully 3D, for example, but manufacturing challenges, power and heat get in the way long before that.
Then you can go ultra-wide in terms of cores, dispatchers and vectors (essentially building bigger and bigger chips), but an algorithm which can't exploit that will be little faster on today's chips than on a 4790K from ten years ago.