First of all, Robert Downey Jr. has hinted around leaving the Marvel franchise. There are reports that his Marvel contract expires with Endgame, and Downey Jr. has other films he's signed up for, like a Sherlock Holmes sequel, as well as a Doctor Dolittle film. The actor told news.com.au, "I just never want to blow it for the last six or seven (MCU movies) I have done by dropping the ball because I decided to go to it one more time. I just want to hang up my jersey before it's embarrassing." This was back in 2017, though.
Second, all of the trailers (save for the final one) show Stark isolated in space, talking into his helmet as a way to send Pepper Potts one final message before he knows (thinks?) he's going to die. "Food and water ran out about...four days ago. Oxygen is going to run out tomorrow morning." He says, "When I drift off, I'm going to dream about you." While we actually do know Stark makes it out of alive (in the most recent trailer we see him marching with the rest of the remaining Avengers fully clad in their new uniforms, it still doesn't erase the fact that much of the trailers have been focused on the possibility that Tony Stark might be a goner.
Redditor teh_vr00m believes Stark will die, and that the scene we see with him recording his message to Potts is actually after a horrendous battle with Thanos:
"My idea is this — the scene with Tony and Neubla working together comes BEFORE he records his final message, I mean this is f**king Tony Stark we're talking about, the dude who made the first Iron Man armor in a cave, with a box of scraps, but like Infinity War showed us, the good guys don't always win. Tony in his desperation keeps trying multiple ways to somehow escape his coffin, but with each increasing failure his mental state gets worse and worse and he finally realizes the terrible truth - he can't escape this one, he's trapped and his hours are numbered and he looks back at his ruined armor and in one final attempt, rebuilds the helmet and records his final words... "Hello Ms. Potts"
In a special feature, we see that Iron Man is back in action...and he actually faces off with Thanos himself. Is this where Iron Man meets his maker? As the OG Avenger, wouldn't it be poetic that he sacrifices himself in order to defeat Thanos and to bring the new Avengers back? It could be an end of an era to make space for the new era of superhero.
