I think you may be underestimating the rate of progress — 100 years ago, transistors were hypothetical, now we have made more of them than there are stars in our past light cone, and they are smaller and faster than synapses to the degree to which wolves are smaller than hills and move further per day than continental drift.

IMO we will probably hit the single-atom limit in consumer devices this decade, though researchers are already suggesting multiple q-bits in a single atom so perhaps we won’t even stop when we get 1Å process chips.

The main limiting factor right now is that we don’t really understand the structure of our intelligence. If you will permit an analogy: perceptrons and convolution kernels are like bricks, while current brain scans (MRI, EEG, etc.) are like nighttime satellite photos of city lights — we’ve got a gap in the middle that would tell us we need steel reinforced concrete to make skyscrapers and why want to build them in the first place.