Avengers 4 - How each characters' story will end

Iron Man: Iron Man is suffering another crisis after losing Peter. It was just like what happened to Yinsen but most importantly his parents. Tony spent at home building machines to fill the void as a metaphor of building a child. However, he regained his will after persuasion from Pepper or Rhodey to team up with Captain America once more but tensions are still high. Later in the movie, Iron Man gets caught in a dream world where things had been different, good or bad is unknown. However, the spirits of Peter, Yinsen and parents moves him to accept that he is Iron Man and doesn't need a huge suit to build around the world as the Avengers are already that suit. With the threat gone, Tony retires and have a child with Pepper.

Captain America: Captain America suffers from losing both Bucky and Sam. He still attempts to mobilize the team to track Thanos and undo the damage. However, Steve blames himself as his actions in saving one man (Vision) caused the deaths of half the Universe. He teams up with Iron Man but tensions still high. Captain America gets caught in a dream world where things had been different, good or bad is unknown. However, the spirit of Peggy Carter moves him to accept that whats inside him, his flaws shouldn't be looked down as without it, Steve wouldn't be what he is today. With that, Cap returns and mended fences with Tony. Captain America retires from the Avengers to found a school for talented individuals.

Hulk: With help from a revived Vision who has some remnants of the Mind Stone's power places Bruce into his mindscape to confront Hulk. Bruce attempts to bring Hulk into the fold but Hulk refuses not because he was afraid of Thanos but afraid of himself, believing he is responsible for why all his friends are now suffering. Bruce realizes that Hulk is more human than thought and persuades him to come out not as a monster but as an Avenger. Bruce and Hulk learns how to undo the damage and to do is a repeat of sacrificing some you cherished as Red Skull stated. This time however, the two found another option and Hulk sacrifices himself to restore the Universe. With Hulk gone, Bruce gets to live the life with Natasha but not before Bruce honors Hulk as a true hero.

Thor: Thor's journey is to get stronger and decides to use Doctor Strange's Sanctum Sanctorum to find answers. There, he learns how Odin became the humbled King. Thor with help from Tony or Eitri built an Infinity Armor to repel the effects of the Infinity Stones. With the war finally over, Thor takes half his people to Earth. At some point in time, he bestowes Stormbreaker to a Korbinite named Beta Ray Bill.
Hawkeye: Hawkeye takes on the identity of Ronin to shed himself from his SHIELD days. His arrows are used to get Ant-Man and Wasp into the dream world and rescue Tony and Steve. He spent the entire defending them from incoming enemies. With the war over, Hawkeye returns to his family.

Black Widow: Black Widow attempts to reconnect with Bruce but there is some bitterness between them due to Hulk leaving her and Black Widow kicking Bruce to get Hulk. Black Widow redeems herself by begging Bruce to not sacrifice himself to undo the changes. Hulk sacrifices himself allowing Bruce to be together with Natasha.

Captain Marvel: Captain Marvel will take charge since neither Captain America or Iron Man are capable in leading the team. Captain Marvel seemingly dies sacrificing herself to save Earth. She survives and leads the Avengers.

War Machine: War Machine will be at the sidelines attempting to calm down the hysteria caused by the Infinity Gauntlet. He attempts to remove the Accords. Even though the Accords are present, changes have been made to allow the military and government to prepare themselves for another attack.

Vision: Vision is revived thanks to Shuri backing up his data. Vision helps Bruce talk to Hulk and later helps Thor understand his journey. Alternatively, he found two boys on the streets and took them in. With the war over, Wanda and Vision adopt the two boys who are revealed to be Inhumans.
Rocket: Rocket bonds with Bruce over themselves having no choice in becoming monsters. Rocket will also build a weapon named 'The Drax' that can remove the Infinity Gauntlet or Stones. He will also show off his piloting skills to get to Thanos.

Ant-Man: Ant-Man will rescue Tony and Steve from the dream world they are in.
Wasp: Wasp will rescue Tony and Steve from the dream world they are in.
Nebula: Nebula joins the Avengers in stopping Thanos and will have her mending fences with Thanos alongside the vision of Gamora.

Shuri: Shuri if she survives attempts to lead the Wakandans to battle Thanos and Black Panther bestowing her the potential role on becoming Black Panther.

Thanos: Thanos lives in peace in the planet he is in. However, he is bothered with visions of Gamora who urges him to give up his quest. As Thanos attempts to stop the Avengers, we learn more about Thanos's past and after bombarded by the vision of Gamora and Nebula urging him to stop, this allows the Avengers to defeat Thanos and Thanos goes for self exile as punishment for his crime.

Post-Credit Scenes:

• An older Cassie comes to the present time to warn them of a greater threat; Kang the Conqueror.
• A portal opens up revealing the ship belonging to the Fantastic Four.