Captain America will die
This theory is very likely because as you may know Chris Evans’ contract is ending after Avengers: Endgame. Chris Evans has pretty much confirmed that he will be leaving with a farewell tweet stating, “Officially wrapped on Avengers 4. It was an emotional day to say the least. Playing this role over the last 8 years has been an honor. To everyone in front of the camera, behind the camera, and in the audience, thank you for the memories! Eternally grateful.”
Now the question is, how will he die? Most people think it will be a sacrifice to help save half the world. Another idea is that in the comics different people take the part of Captain America. Some people believe that if Captain America dies, either Falcon or Bucky Barnes will take his place as Captain America. It is more likely that it will be Bucky because he is long time friend but Falcon has a pretty good chance as well.
In the trailer for Endgame, loads of fans have noticed the dramatic hair change between the Avengers, more specifically Black Widow. Could this be due to time travel? In parts of the trailer her hair switches from long red hair to long blonde hair to short blond hair. In Avengers: Infinity War she has short blonde hair and then in parts of the Endgame trailer she has red hair. Fans also believe this is why most Avengers have had dramatic hair changes in the recent movies, Captain America growing an awful beard, and Stan Lee’s cameo giving Thor a haircut in Thor: Ragnarok. This is where the Quantum Realm comes into play.
The Quantum Realm was a major part of Ant-Man and the Wasp, a movie coming out after Infinity War. The movies shows Scott Lang and Janet van Dyne crossing through the quantum realm after being stuck there since 1987. Once rescued, Janet tells her daughter Hope and husband Hank all about the power of quantum energy. Later they send Ant-Man back into the realm and he gets stuck there, and in the post credits scene Hope, Hank, and Janet get dusted by Thanos.
In the Endgame trailer it's revealed that Scott Lang has escaped the Quantum Realm and goes to the Avengers facility. Captain America says “Is this an old message?” as he is watching a video of Scott banging on the door. This leads fans to think that when Lang escapes the quantum realm, he accidentally ended up in the wrong time period.
One thing Scott doesn’t know, is that Thanos destroys half the universe. Some people believe that Lang will go back through the realm to meet up with present day Avengers. Then after that they will use the quantum realm to their advantage to save half the universe.
If that proof wasn’t enough for you then there is more proof from the guy who spoils everything, Tom Holland. In an interview with Benedict Cumberbatch and Tom Holland, the interviewers ask a question on who messes up their lines more often. Benedict Cumberbatch admits it is him and Tom comes to his defence and says, "He has the most difficult lines though. He has to talk about so much Quantum Realm stuff. I just have to talk about, ‘Yeah, man, that’s awesome!’ So mine is easy but his is so difficult!" This proves that the quantum realm will be mentioned in Endgame because Doctor Strange never mentions it in Infinity War. However, Doctor Strange got dusted by Thanos, so how will he mention the quantum realm if he is gone?
Doctor Strange Time Loop
After watching Doctor Strange once again, I am pretty convinced that Doctor Strange has been lying during the whole entire movie of Infinity War. Around the end of the movie when Doctor Strange is on Titan with a few other superheroes, you see him use the time stone to view around 14 million ways of how Endgame ends and that only one works. This makes us believe that the 1 possible way requires Doctor Strange giving Thanos the time stone. However, in Doctor Strange the movie tells you the limitation of the time stone, one of them being that the user is not able to see past their own lifespan. This means that he could look as far into the future as he wants, but he wouldn’t be able to see past the moment he got dusted.
Although Strange does find a way around the limitations via time loops. This means if he really saw the way the Avengers defeat Thanos,he made a time loop. Now the question is, when did he start the time loop?