If Poland plays their cards right, they're getting a lot of real estate in the upcoming deal.
If they back the wrong horse? Breslau, Stettin, Danzig, Allenstein, Elbing, Tilsit, even Memel - all up for grabs.
If I'm not mistaken, those cities were purged of most of their German populations right after WW II. For the sake of argument, what would Germany do if it somehow regained those cities? About the only way Germany could control them is by martial law.