Let say Duke Johann Wilhelm produce a child, or his older brother survive long enough to get married and produce child.
What effect would this have on Brandenburg, Elector Johann Sigismund still inherited Prussia from his father-in-law, but Brandeburg lack its Rhinelandish possesions. In OTL the Brandenburgian electors already befor Johann Wilhelm death adopted the policies to increase their influence in west, while giving the noble increasing power until the 30YW. What would happe if they was forced to focus on their poorer but bigger and heavy populated easten possesions?