From reading everyone's comments it seems to mainly come down to the sense of occasion and simply how special the Z4 M is, that's why they havent chopped it in for something newer.
Having not known about Z4's really up until a couple of years ago, I wasn't even a fan. Didn't like the shape or the interior.
However, after revisiting and having a proper look they really grew on me.
The M version is a special car. Something you don't see many of and something that people take a second look at or turn round when they hear it because it's something a bit different to the usual sea of Boxsters.
Having not known about Z4's really up until a couple of years ago, I wasn't even a fan. Didn't like the shape or the interior.
However, after revisiting and having a proper look they really grew on me.
The M version is a special car. Something you don't see many of and something that people take a second look at or turn round when they hear it because it's something a bit different to the usual sea of Boxsters.