Maybe for newer devices, but I highly doubt they do that for older tech. Having multi-million $ fabs stopped will make them lose a lot of money, specially nowadays.
ATmega328 dates back to 2002! So do a lot of other mcus.
This can be easily seen: Devices that have been +6 years on production are easily sourced, while newer designs (ex. PIC18-Q10 family) are gone and estimated for DEC-2022!
I might be wrong, but that's what it seems to me, so I would stick to older tech.
Even stm32 isn't that edge cutting: they started to use 40nm in their H7 series in 2016.
A lot of their product line still use 90nm, which is a 2003 technology. In 2005 we already had 65nm.
Most mcus don't need such ridiculous high density fab process, their transistor count is low compared to modern computing.
So relying on older fabs process keeps costs down, I guess. These plants already payed themselves years ago.
I keep thinking that this semiconductor crysis is partually faked to riuse the prices.
Yeah, TSMC might be completely overloaded with all phone/cpu/gpu new tech stuff, but c'mon, the're hundreds of fabs using older tech.
Not everything is GDDR5, Nvidia/AMD and 3D-NAND.