I think you underestimate how hard it is to move from Mypy to Pyright in big codebases. Having something very very close to Mypy should be very interesting for some companies with 1mLoC+. Relative maturity can still be a reason for 1-2 years and I have no idea what to do at that point.
Relative maturity can be a reason for quite a while (people overestimate how far Pyrefly and Ty are).
Relative maturity can be a reason for quite a while (people overestimate how far Pyrefly and Ty are).