No, the Magyars could not end up in Prussia. There is no way, because Prussia has no steppe lands for the Magyars' horses.
They definitely could have settled in Bulgaria: if the Magyars had won at the Battle of Southern Buh, IMO they would proceed to subdue the Bulgars and take their place in the region.
But failing that, there is not much elsewhere the Magyars could go with this late a POD.
Pannonia was great because it was the largest steppe in Europe, perfect for the tens of thousands of semi-nomadic Magyars, and their animals. Come to think of it, maybe after destroying Bulgaria, the weakened Magyars are overrun by the Byzantines and deported to Anatolia. There is some steppe land there, so perhaps they could make their home in the highlands (a random idea I had).
As for going further west, they did so
in OTL. But again, most of Europe is poor land for steppe warriors, so they would not be interested in settling Germany or the Alps. Bulgaria and Hungary are probably the two areas farthest west possible.
But anyway, my favorite idea has always been WI the Magyars don't migrate west at all, staying in the area of OTL Moldavia and Kiev.