Full spoilers ahead for Avengers: Endgame!
The screenwriting duo of Christopher Markus and Stephen McFeely shot down several fan theories in a recent spoiler interview promoting Avengers: Endgame.
In a lengthy chat with The Hollywood Reporter, the screenwriters dismissed the notion that there was any other way for the Avengers to defeat Thanos other than for Iron Man to sacrifice his life:
Source: IGN.com Endgame Writers on Whether Those Characters Are Really Dead