The first trailer of Avengers: Endgame had an injured Iron Man lost in space post the Infinity war and recording a message for Pepper Potts. With a broken armour, it looked that his return will be difficult. However, in the TV spot aired during Super Bowl fans saw him prepping up for his return with Nebula. Since then, fans have been rooting theories on his return and his mission to beat Thanos.
A new fan theory on Reddit suggests that Black Panther's sister Shuri will be key to save the two stuck in space. The user wrote, "I believe Shuri went into hiding after the battle of Wakanda and is currently leading the country from the shadows. That would explain why she’s assumed dead. I’m not sure what the reason for her to go into hiding would be, but I can’t think of any other reason she would be listed as ‘missing’ and yet still be alive."
(A still of Iron Man and Nebula from Avengers: Endgame teaser)
The user points out that Shuri was working on Vision and mind stone before Thanos' army breaks out in Wakanda. And since Vision is connected to Jarvis, there are possibilities that she was able to connect some of his memories to the server enabling her to connect with Iron Man in space.
Talking about the Super Bowl TV Spot, the new teaser had the Avengers planning for the big war that lies ahead of them. Apart from Iron Man and Nebula space appearance, on Earth, we see Captain America, Thor, Rocket, Black Widow, the Hulk, Ant-Man and Hawkeye among other living Avengers training and mapping out their strategies to beat Thanos.
With posters like "where do we go, now that they are gone," Marvel teases the end of Avengers Universe in MCU.
Marvel's last Avengers film, Avengers: Infinity War took the audience in a state a shock when Mad Titan acquired all the Infinity Stones and wiped half of the universe with a snap of his fingers. In the climax scene, Doctor Strange goes on his expedition of 14,000,605 outcomes to defeat Thanos and ends up with only one possibility that will lead the Avengers to save the universe.
At the end of the Infinity War, Captain America, Iron Man, Black Widow, Hulk and War Machine were among the few Avengers who survived Thanos’ snap. While Black Panther, Spider-Man, Nick Fury, Doctor Strange and Scarlet Witch among others disintegrated into dust.