A silicon atom is about 111pm. So 90 atoms is 10nm. What is the minimum size of a feature in atoms before running in to problems with physics?
About 10nm. High-end chips have been there for ages now. Fighting those problems takes quite a bit of creativity.
That means that practically, the smallest conceivable metal pitch is 10nm, the smallest gate is 20.
From 5nm, it implies a factor of 10 is left, or about 3-4 nodes.i expect lower scaled nodes at larger delays, but another 15-20 years.