You are talking about fundamental physical limits? Um... No, [1]
"At about 26-28.5 minutes of the Jim Keller:
Jim notes that transistors could reach 10 atoms by 10 atoms by 10 atoms while avoiding quantum effects. People are also working on harnessing quantum effects."
We are so far away from fundamental limits. That even if we assume we could somehow double transistor density every two years, which we dont anymore, there are still at least another 15-20 years before we are close to that limit. And that is not accounting any 3D Transistors.
Realistically we already have Roadmap up to 2030 from TSMC. The only limit we will hit is that the node is too expensive and market could no longer afford the premium. Which You could expect to happen within next 10-15 years.