In reality I really don't think it is plausible that all of these realms could unite in personal union under one King; his resources would be stretched way too far and at length an opportunist(s) would be able to displace him from one throne or another. You have various Geminind princes, descendants of the Piasts and Arpads, as well as foreign powers, all of whom could attempt to get a slice of the Jagiellon pie, to the exclusion of Louis' son. Albert of Hohenzollern, of Prussia, would especially be in a good position to make a bid for the Polish throne (his mother was a Polish Jagiellon princess).