3. Everyone’s Trapped in the Soul Stone
This is a theory we’re ranking high on this list not just because it seems like the direction Marvel would take after showing Gamora being in the Soul Stone at the end of Infinity War, but would also allow all the departed characters to still have roles in Avengers 4 despite still technically being dead. Think about it: how much of a bummer would it be if Avengers 4 has a much smaller cast than Infinity War because half of the characters are dead? Yes, there will be new characters such as Captain Marvel and we’ll probably see Ant-Man, the Wasp, and Hawkeye too, but to go a whole movie without the likes of Spider-Man, Black Panther, Star-Lord, and Drax (not to mention everyone else turned to dust by Thanos’ nasty scheme) would be kind of a drag.
There are all sorts of ways Avengers 4 could present this, but having the Soul Stone act as some sort of afterlife/purgatory would make the most sense and with the souls all still intact inside of it, bringing some or all of those souls back would make narrative sense, though that’s probably still going to take some sacrifices on the part of the remaining living heroes to pull off.
http://www.ladbible.com/entertainment/film-and-tv-avengers-infinity-war-co-director-confirms-soul-stone-theory-20180507 Source: LADbible
2. Cap Makes The Ultimate Sacrifice
Many people assumed that Infinity War would end with Captain America’s death, as Chris Evans has made no secret that he plans to walk away from the role after the current crop of Avengers films. However, Steve Rogers is one of the heroes spared from the Infinity Gauntlet, setting him up to play a big role in Avengers 4. In fact, the entire original six Avengers team is still intact heading into Avengers 4, which means that Cap and Iron Man are going to be working side-by-side once again, only this time the fate of the entire universe is at stake.
This is perfect fodder for finally resolving the feud between Steve Rogers and Tony Stark and what better way to do that then for one of them to prove his love and loyalty to the other by sacrificing themselves? Cap mentions that the Avengers “don’t trade lives” when Vision brings up the idea of self-sacrifice in Infinity War, but Steve Rogers wouldn’t hesitate to give his life to save Tony … or give him the power to bring their friends and loved ones back from the dead. Yup, Cap’s giving up his soul so that Iron Man can wield the Infinity Gauntlet and fix everything, thus opening the door for someone else to take over as Captain America in the MCU’s next phase.