As we saw with 7nm chips making them smaller doesn't necessarily mean better efficiency. Right now most 10nm chips are way more efficient than any 7nm out there. Also with smaller chips you run into issues like overheating, too many propagation errors which end up making them less efficient and slower.
I think with 7nm we are already pushing the limits of silicon chips.
The chips were not using silicon I think they use gallium or I read the article wrong.
and the most efficient gear right now is a 7nm the s15.
But I think there is a lot of improvement on the 7nm chip before we move on to a 3 or 2.5 nm chip.
If the m10 whatsminer does 60 watts a th on the 16nm chip on low speed high efficiency
and the bitmain s9 does 80 watts a th on the 16nm chip on low speed higher efficiency
which is true. the 16nm is maxed or close to maxed for efficiency .
the bitmain s15 is doing 50 watts a th on low speed on a 7nm chip
a 25% improvement on that is 37.5 watts a chip.
since the m3 was 150 watts a th vs s7 250 watts a th 28nm chip
the m10 was 60 watts a th vs s9 80 watts a th 16nm chip
the m? should so 37 watts a th vs 50 watts a th for the s15. 7nm chip
so if we do get a good 3nm to work I would guess 5 years from today and 25 watts a th