Current expansion / investment plans for TSMC are mainly for
1. Bringing up volume of N5 up to N7 levels, which according to the roadmap below is till end of 2023. Including American fab
https://fuse.wikichip.org/news/5760/tsmc-2021-foundry-update-foundry-roadmap/
According to this data, N5 is less than half N7 output which is definitely nowhere near enough.
Already booked all the way to end of 2022 according to earnings report.
Currently Fab18 is doing N5, It is like Phase 3 of expansion going on I believe.
2. Ramping up N3
Don't know where this is, probably Fab18 due to more recent EUV equipment installation there.
3. Building new fabs for N2 and beyond
Fab 20
I guess N7/N6 will take over the role of 16FF, once it becomes cheap enough.
Fab 14 and 15 are doing some form of N7/N6 (excluding Fab12A,12B which were doing some limited production and research)
N7 family capacity would no longer be expanded after end of 2021 as per TSMC roadmap
The leading edge nodes would continue to remain dear for the foreseeable future.
Post 2024 It is GAAFET/MBCFET era. Don't know what it will bring. If it is as good as touted by everyone, everybody will be jumping on it.