There are three Important points about its vanishing in Public life

The first means that it isn't :

The surviving former german population of the Prussian territories east of nowadays Germany blended into the german society but still some of them are organized in "Landsmannschaften" or "Vertriebenenverbänden" most of which are Members of the "Bund der Vertriebenen" which doesn't mean that al of the members are revisionists or revanchists some really are just there to keep cultural traditions.

Second point would be that, beside the inhabitants of the former Order-state at the baltic sea which now is named "Oblast Kaliningrad" which were the original Prussians, a nation with a baltic language wich was mostly lost in the last centuries so that they were traded as Germans, Prussia wasn't a Nation but a State; a so called "Multinational-state" or "Vielvölkerstaat".

The people who identified themselves as Prussians is a completely different case; I know a polish Woman living in Berlin, maried with a Kurdish man who claim herself to be Prussian and so are her children and so their father(he smiles), i would agree, but most people with the prussian eagle on their car wouldn't. The Prussian Identity is something like a hidden battlefield filled up with a lot of contradictions but since it is absolutely pointless to argue about belonging to a state that doesn't exist and will probably never exist again i think from the point that Prussian identity was bound to enlightenment and rationality it should stop, but as it bound to tolerance to i wouldn't try to stopp others from continuing.