So in a nutshell , a prussian communist republic is created after ww2. Same borders as the former province with perhaps the area east of vistula(mariemburg) with the capital as konigsberg.
When the Soviet Union die , Prussia stay indépendant (like Austria) so no union with Germany , let's even say i doesn't go to the european union right after the fall of ussr.(give him 4,5 or even 10 years). The country is german speaking but it gets more influenced with the baltic and polish culture as time passes.
So is this possble ?