Clearing up a lot of the mystery surrounding next year's Avengers 4, Redditor abigfriend has revealed what they claim to be leaked plot details about Avengers 4. While these sort of leaks tend to be hit or miss on whether or not they are true, the information revealed matches up perfectly with the other movies in the franchise and of the leaked set pictures. Regardless, all of these "leaked" details should be taken with a grain of Peter Parker soul dust. Warning: potential spoilers for Avengers 4 lie ahead.
According to the Redditor, the main plot of Avengers 4 will feature the remaining Avengers travelling back in time using Hank Pym's Quantum Realm technology that will be introduced in Ant-Man & The Wasp next month in order to retrieve the Infinity Stones before they got into the hands of Thanos during Avengers: Infinity War. However, Thanos will learn about their plan and will start following the Avengers through space and time in order to stop them, learning more about the Infinity Stones' combined powers as he goes.
According to the report, the original Avengers will receive most of the spotlight in Avengers 4, in addition to focusing quite a bit on the relationship between Thanos and Nebula. Apparently, Thanos and Nebula will receive the same focus that Thanos and Gamora received in Infinity War. Thanos will still refuse to care about Nebula and will try to manipulate her by pretending to care. Apparently, once Nebula gets her hands on the Soul Stone, she will learn more about its powers and actually use them against Thanos after realizing he was deceiving her.
"Previously, it was believed that the only way to unlock the power of the soul stone was to sacrifice something you loved, however the opposite is also true: a sacrifice of something you infinitely hate can also unlock the powers of the Soul Stone. Guess who hates Thanos more than anyone in the entire universe? Yup, Nebula... Nebula traps Thanos into the soul stone."
The final battle of Avengers 4 will supposedly mirror the final fight in Avengers: Infinity War by taking place in Wakanda. However, this time it will feature all of the heroes, including Iron Man, Nebula, Hulk in his actual Hulk form, and all of the Avengers that turned to ash at the end of Avengers: Infinity War.
"The final battle will be a revisit to the third act of [Infinity War]. [Infinity War] was the "bad ending" where Thanos won whereas [Avengers 4] will be the "good ending" where the Avengers win... This alternate timeline Wakanda scene is where every superhero will fight together for the "money shot"... At this point in the Wakandan battle, Thanos no longer has the infinity stones yet still manages to put up a fight against the Avengers using brute strength."
Finally, one enormous detail that a number of Marvel fans will be devastated to learn is the supposed death of one of the most notable Avengers.
"There is a scene where Tony and Cap are off stealing the Tesseract from Avengers 1 era and Thanos is about to catch Tony and kill him. However, Cap says he will fight Thanos 1v1 to buy Tony more time to escape. Tony says that he will die fighting Thanos and that they should stick to their plan of escaping, Cap responds saying "This was always the plan." THIS SCENE IS A CALLBACK TO THE SCENE IN IRON MAN 1 WHERE YINSEN SACRIFICES HIMSELF TO ALLOW TONY TO ESCAPE."
This scene description fits perfectly with some of the leaked set photos from Avengers 4 that showed both Captain America and Tony Stark in the middle of the New York battle from The Avengers, each with some sort of time-travel-looking device on their hands. Not only that, but the death of Captain America would make sense, considering that Chris Evans' contract ends after Avengers 4.
One last major detail that the Redditor shared was that Avengers 4 would further expand on the alien species known as the Skrulls, who will appear before Avengers 4 in Captain Marvel. According to the leak, the end of Avengers 4 will set up the Skrulls to play a much larger role later in the franchise.
"Because the timeline of IW was altered in A4, this is how Marvel plans on introducing the Skulls and secret invasion by already having the Skulls exist on Earth secretly in this alternate timeline."
All in all, these details from abigfriend are exciting and make a lot of sense. Unfortunately, there is a great chance that all of these details were faked simply for attention. Only time will tell if this is how Avengers 4 actually pans out, but based on what we know so far, this leak does make quite a bit of sense. Avengers 4 will release in theaters on May 4, 2019.