Sigismund controlled significant hereditary lands---Hungary, Croatia and Bohemia, the latter in personal union, but still, they paid taxes to him. He was OTL the richest and most powerful emperor until Charles V. What I'm wondering is, can his successes continue under a male heir, and for how long can the Luxembourgs remain on the throne? Basically, is a Habsburg resurgence inevitable, or can they be butterfly'd away---basically, reduced to the stature of the Wittelsbachs, or some similarly eminent-but-not-dominant house.
As long as the Luxembourgs have adult male heirs, then they are in a good position to keep the throne. A Habsburg resurgence is not inevitable, though they could obtain the position as the first behind the prince-electors in the order of precedence (one of the things claimed by Privilegium Maius) and maybe eventually an electorate way down the line.
My TL has Sigismund inherit Bohemia about a decade sooner, and elected and installed as emperor about twenty years sooner than OTL. He is also elected to the Polish Crown after Jogaila dies at Grunwald. In other words, he's even richer and more powerful than OTL. I'd like to give him an heir and have that heir get elected to the throne as well, but I think there ought to be an interlude of some kind to break things up a bit. I want Sigismund to die and have a Habsburg get elected, but then I want his heir to take over. I need to know if that's doable, or if the Habsburgs, once back in power, will stay on the throne for good.
Throwing in the Polish Crown is a bit too much, IOTL Mary getting Hungary-Croatia and Jadwiga getting Poland was deliberate, since AFAIK the Polish nobility wasn't happy with the personal union.
The house of Luxembourg with Bohemia & Hungary-Croatia as their Hausmacht will be able to be re-elected again.
The Habsburgs in the long rule would need something like the OTL Burgundian Inheritance to become a significant counterweight again.
Also Rudolf I of Habsburg didn't manage to pass the crown directly to Albert I of Habsburg, who's reign was cut short since he was murdered by his cousin John Parricida (though to be fair his uncle Albert basically stole his inheritance); this paved the way for the rise of the house of Luxembourg. Then the house of Luxembourg needed to go extinct and the (Albertine branch) house of Habsburg being their heirs for the Habsburg to regain the throne.
Personally TBH I find the career of the houses of Habsburg and Luxembourg after the Great Interregnum rather interesting. The house of Nassau with Adolf of Nassau shows, that making the leap from a prominent comital house to one of the important dynasties of the Empire wasn't guaranteed by being elected king of the Romans. AFAIK Adolf of Nassau initially had slightly more modest aspirations, since he bought the landgraviate of Thuringia and seized the margraviate of Meissen as an reverted imperial fief. However expanding there brought him into conflict with Bohemia, Mainz and naturally the Wettins, and he also managed to antagonize both the Wenceslaus II Premyslid king of Bohemia and the Albert of Habsburg duke of Austria & Styria (Adolf's successor as king of the Romans after Adolf was deposed).