Captain America 4
Although this movie has not actually been confirmed but highly rumored multiple times. The lack of an announcement for a Season 2 of Falcon and the Winter Soldier basically confirms it and it makes sense because Sam Wilson is no longer Falcon he is Captain America. It's safe to assume Bucky will be returning because in Captain America movie so far there's also Bucky. We can also assume that Sarah Wilson will also be returning as she and Bucky begin flirting a lot more to Sam's chagrin. Maybe Sam can return the favor later by flirting with someone that makes Bucky uncomfortable? As long as we get more hilariously awkward moments like this one I am all in because Anthony Mackie and Sebastian Stan just might have the best chemistry in the MCU. It leads to the question of what can we expect from the 4th Captain America movie?
Sharon Carter has been reinstated by the US Government but she will still likely remain the ruler of Madripoor especially considering no one knows she is the Power Broker just yet.
Although she very well could be in this movie, I don't see her playing any role that we haven't already seen from her in Falcon and the Winter Soldier as the Secret Villain, and if anything she seems more likely to appear in future MCU projects like ArmorWars when she will begin selling Stark Tech to villains.
We heard Kevin Feige state that he would love Alexi Shostakov AKA Red Guardian (played by David Harbour in Black Widow). Red Guardian spoke about facing off against Captain America that everyone seems to be writing off as a lie that he couldn't have fought Steve Rogers because he was frozen ice, but after he was frozen in ice what did the US Government kept doing? They kept trying to recreate the formula and as we learned from Isaiah Bradley as he became the second Super Soldier. Considering he met Bucky before then it's not to far off to assume that he had gone on other missions as Captain America but he was imprisoned shortly after. The Falcon & Winter Soldier show takes place in 2023 after the snap and Isaiah was tested in the 1950's assuming he was 20 and then they put him in prison for 30 years putting his release in the 1980's where his death was faked and he was secretly relocated to Baltimore, Maryland.
So one of Isaiah's missions was probably to Russia at some point and Isaiah ran into The Red Guardian there (before either were imprisoned by own their own Governments). Since Red Guardian didn't go into detail and he was incarcerated himself he could very well have meant Isaiah Bradley not realizing the Captain America everyone was talking about was actually Steve Rogers. As we know Red Guardian had received Super Soldier serum at some point in the 1980's as we saw in Black Widow, so perhaps Isaiah had to make a deal to get his release from Prison and then had to fight Red Guardian and since Red lost the fight Russia imprisoned the him for losing.
So where does the film begin?
We pick up in modern time as Red Guardian is now obsessed with having a rematch with Captain America (assuming its Isaiah Bradley) following the events of Civil War and the Snap. Meanwhile Bucky faces off against a spy who keeps beating all of his tricks and then eventually tracking them down only to find out they are also a Super Soldier whose identity will be later revealed. Including Red Guardian in the next Captain America movie makes sense because of his relationship to Bucky, although Bucky would have been brainwashed at the time, if they had in fact met before it will be a hilariously awkward conversation as Red Guardian assumes they are friends/acquaintances and he may even reveal a few more secrets to Bucky about himself that he doesn't remember.
Sinthea Schmidt AKA Sin is the Daughter of the Red Skull and she is rumored to be the Villain in the next Captain America movie. The only issue with this is that makes her very old at this point considering the Red Skull disappears in 1945 so that would mean she has to at least be 70's years old. In the Comics Sin does not have the benefits of inheriting the Super Soldier Serum from her father (the Red Skull). So to make a juicier story though Sin could have seduced Bucky (when he was the Winter Soldier) at some point in the 1990's in order to have a child with him in the hopes that she can give birth to an heir that does have the Super Soldier serum. Thus leading to the next big bad villain is actually Bucky's Daughter.
So how does the Red Guardian fit into this?
Well we don't know when Red Guardian first received the Super Soldier Serum but we only this happened at some point during the Cold War. The question is how would Red Guardian know this secret other than Russian's intelligent network?
We do know that as of 1991 he was no longer operating on missions and the next year he was assigned to go undercover raising Natasha and Yelena until 1995. So what triggered the Russian Government to bench the Red Guardian and did the Russian Government actually recreate the Serum or were they gifted it? Sinthea Schmidt (Red Skull's Daughter) likely had a role in H.Y.D.R.A during the early 1990's or at the very least had connections or she spy crafted and stealing the remade Super Soldier Serum that H.Y.D.R.A was perfecting (before or) after they created the additional Winter Soldiers (from Civil War). Sin takes the formula to Russia working with scientists there to perfect it as she is looking for the perfect specimen to give the Super Soldier Serum to so that she can pass the Serum on to her child (but then maybe they realize they are related) or things get awry when (Captain America - Isaiah Bradley?) arrives (or just a fault out of trust between Russia and H.Y.D.R.A occurs) leaving Sin with one last option and that is the Winter Soldier (AKA Bucky). Sin breaks him out and for a bit of time they live together but before long the Winter Soldier is needed once again for a mission. After failing to make more Winter Soldiers and ties with Russia were strained at best H.Y.D.R.A puts pressure on Howard Stark to help recreate the Super Soldier Serum he declines and the Winter Soldier is sent to kill Howard and Maria Stark and then put back on Ice.
Will Elijah Bradley make an appearance as well? Perhaps inspired by Sam Wilson as the new Captain America he begins becoming a hero himself. If this movie will be like the recent Captain America movies, we can expect a huge cast and would likely also bring back Isaiah's grandson Elijah Bradley as well as a minor story plot to progress his character along. Possibly even incorporating his Young Avengers story line where he takes a Mutant Growth Hormone that eventually leads him to gaining the Super Serum Soldier for himself (see Young Avengers article for more).
A few other ideas could be depending on the scope and size of the movie could be Sam Wilson leading the newest roster of Avengers vs. the Russian Avengers (AKA The Winter Guard) or even leading the Avengers vs. the Dark Avengers/Thunderbolts but that seems less likely given that John Walker respects Sam but its the MCU he could always end up being manipulated by Sin to cause more chaos.
Red Guardian was telling the truth and he did actually fight Captain America but it was Isaiah Bradley and then they get to re-meet as retired heroes. The movie can end with Sam flirting with Bucky's Daughter to drive him crazy after Sam had to watch Bucky flirt with his Sister all movie, Bucky and Sarah then one up him by telling Sam that they are engaged. Let us know what you think, would this be a good enough plot twist for Sam and Bucky or do you expect more from the MCU?