As I told you before I’ve read many fan theories for Avengers EndGame. This one can be one alternative possibility. Tony Sacrificing himself to defeat Thanos.
A Reddit user SpikesMountainDew has his theory for Avengers EndGame. He says that when Thanos arrived at Titan with the soul stone he said his famous dialogue, “The hardest choices requires the strongest will”. Where Doctor Strange figures out that he has sacrificed Gamora to get the soul stone.
Beacuse he has seen 14 Million possible futures Everytime to get the soul stone Thanos would have sacrificed Gamora. And then if we dive deep into the words, Doctor Strange says, “Then you’ll find our will equals to yours”. This line says that if Thanos has sacrificed his best than they(Avengers) are also ready to do so. And one one who sacrifices will be Anthony Edward Stark.
Doctor Strange saved his life and gave the Time Stone. He knew that when Chitauri attacked on New York he was ready to sacrifice, when Ultron attacked on Sokovia he was ready to do the same and now he will do that again. Either way Tony will be a sacrificer or Sacrificee but will have to do it to win against Thanos.