http://www.pentaxfans.net/thread-138657-1-1.html
(in Traditional Chinese, but posted pictures are self-explanatory.)
So, the hotshoe base material has been changed, from plastic to metal. The PCB inside/underneath has been updated too. It can be seen that the whole circuit board design has completely been revamped.
Speaking of those Metz flashguns for Pentax, last time they released an update of the firmwares for their newer models that enabled the HSS on the newer Pentax bodies but there existed a major bug that caused the A and M modes disabled. They soon released an updated version of 4.1 which contained the bug fix very shortly. For instance, the following link is the firmware download page for the 58 AF-2 flash:
http://www.metz.de/en/flash-units/firmware-download-flash-units/mecablitz-58-af-2-digital/pentax.html
After the above was released, I have checked on the web for the feedbacks from some Pentax users that the firmware update does work for them and there is no other major bug and issue found and reported so far.