I agree that it is improbable that the war in Europe would end in 1945 in this scenario, but let’s put that aside for a moment. Whatever year the Germans surrender, the Western Allies will probably not allow Poland to annex near as much German territory. After all, it was Stalin who pushed for the Oder-Neisse line, and even then he only did so late in the war. This means that much of the flight and expulsion of Germans from Poland that happened in our timeline will not happen here (though what happens to the Sudeten Germans is an open question). Poland probably gains East Prussia (all of it - no Kaliningrad Oblast) and part of Silesia.