Yekke2
In the Torah by the Avos and Moshe Rabbeinu and Aharon it says “vayigva” which means they died a missas neshika from Hashem no malach hamaves involved.
Regarding the future, Im not so clear on the sequence of events but its likely that ghe shechting of the malacha hamaves will be at a later time than the building of these arei miklat. Btw is this future arei miklat discussed?