I agree this is a real concern- it's not just about not needing teaching to be an attractive profession long term, it's also about the loss of expertise from the profession. In more and more schools we are seeing people become HoDs only a few years in, and SLT maybe less than 10 years in. I'm not saying this is always an issue, but I think it often is, and can lead to all sorts of problems in those departments and schools.
It's even worse when people are pressured to take on responsibility they don't want or don't feel ready for.
As an example, I have a friend who qualified as a physics teacher not that long ago. In his first year of teaching, he was teaching Y12, Y13, and multiple Y11 classes. In his second year of teaching, he was pushed into a "head of physics" role he didn't want. By his third year of teaching, he was burnt out, and he left the profession.