What if Stefan Dušan had not died so suddenly in 1355?

[Enigmajones]

I was just reading about the Serbian Emperor Sefan Dušan and how he conquered and established a powerful empire centered on Serbia, which at it's height controlled most of the Balkans. In 1355, he raised an army of 80,000 men with intent on marching on Constantinople, and 40 miles to the east of the city, when King(Emperor?) Stefan died of a sudden illness. But the question is, what would have occurred if the Serbian army had assaulted Constantinople? Would Stefan be able to enforce the submission of even more of the region? Or would his army have been broken by some other fashion.

Also, I understand, that if Stefan dies in battle, his weak son would succeed him, which would probably be not a good scenario to ensure the survival of the Serbian Empire.

 

[Fabius Maximus]

Constantinople was a pretty tough nut to crack, but the Byzantine Empire was in a bad way, so unless some other crisis arises and calls the army away I expect Stefan to take the city. He'd probably adopt the title Emperor of the Romans afterwards, perhaps creating a mixed Serbian/Greek polity.

 

[Enigmajones]

Constantinople was a pretty tough nut to crack, but the Byzantine Empire was in a bad way, so unless some other crisis arises and calls the army away I expect Stefan to take the city. He'd probably adopt the title Emperor of the Romans afterwards, perhaps creating a mixed Serbian/Greek polity.

Just researching this more and it says that he intended on forming an alliance with the Ottoman Sultanate through marriage, would this have helped him?

EDIT: Just a note, his name was Dusan not Stefan, my mistake.