Prussia was Germanized because its inhabitants remained pagan, and when the Baltic Crusades began they were wiped out. For the same to happen for Poland, then Poland could not already be Christian. Of course, if Poland was not Christian, then it'd be incredibly hard for the Germans to push east. A major reason why Germany was able to germanize the western slavs in their lands is that Christian Germany and Poland were hammer and anvil to them, and they were isolated and overwhelmed.
It's conceivable that at some point, a pagan Poland would be defeated and germanized, but only because while the Germans attack in the west, the Orthodox Russians attack from the east. At which point, most of eastern Poland become Russified. It is also probable that Bohemia expands as well taking much of Poland, or at least the area around Krakow. The area of Poland to be Germanized would probably be a lot smaller than you suppose.