Mild spoilers for Harry Potter and the Cursed Child. As I don't have a copy to hand, nor intend to touch one again, I can't provide exact quotes.
As I recall, one of the premises in Act 3 is as follows:
- Due to some time travel shenanigans, Neville died in the battle of Hogwarts.
- Because Neville died too early, Nagini survived the battle.
- Because Nagini survived the battle, Harry died (by Voldemort's hand?) when he faced Voldemort.
How does this last point make sense? From what I understood of Deathly Hallows, Voldemort's remaining number of Horcruxes has nothing to do with him being or not being able to harm or be harmed by Harry.