I'm seeing a lot of brilliant theories at the moment regarding the MCU yet surprisingly no-one has yet touched on what's next for Bucky, but I've got a few hunches on what's to come.
Now most of this theory stems from Sebastian Stan's 9 film contract with Marvel, of which he is now 3 down, 6 to go. We're going to assume for arguments sake that Infinity Wars are going to be classed as 2 separate movies as far as contracts go, though no-one is entirely sure thanks to Marvel's secret ways.
Be warned, there will be some spoilers during this article, so if you're reading this and somehow haven't seen Civil War yet, I'd maybe not read on. If you're all caught up, get ready for this one.
We've watched Bucky and Steve's journey over the last few Cap films and watched as Bucky has swapped from the protector role to the protected thanks to Steve's amazing ability to never give up on his old friend and see through the brainwashed murderer he has become. Civil War finally saw the two soldiers back together and fighting for the same side (for the most part anyway) and we ended with Bucky accepting he will continue to be a danger until he can be fully free of the Hydra brainwashing, choosing to go back into cryo-stasis with help from T'Challa and his Wakandan lab.
Now it's going to be pretty difficult to gloss over Bucky being in stasis in Wakanda during Black Panther so it's safe to say he's probably coming out of stasis at some point during this movie, be it in a damaging attack to T'Challa's compound or even a situation where the Black Panther needs a helping hand... Or helping metal arm as it would be. One would assume that someone at the labs would have developed a Vibranium arm for Bucky at some point, ready for when he comes out of that chamber.
Once Bucky is back in action we can move on to Infinity Wars. After setting up Zemo in Civil War as a regular human being rather than the Adhesive X covered Baron Zemo we all know from the comic books, we saw the very beginning of his character, his hatred for Captain America and his incredible (and terrifying) mind creating a hugely elaborate plot to turn the Avengers against each other, presumably thinking that Cap wouldn't be able to fend off the other Avengers and their abilities. This is where Marvel have been clever, instead of the villain being killed at the end of the film like we may be accustomed to, we actually see T'Challa sparing his life in favour of justice. Because of this, Marvel still have plenty of scope for him to progress into the familiar villain we were expecting to appear in Civil War. I mean come on, Bucky broke out of that chamber already, it's not out of the question that someone else could break out of it again. Granted Bucky did have that metal arm, but what's to say Zemo isn't going have outside help?
Infinity Wars is going to see a furious Thanos scrambling to get all the Infinity Stones quick, more than likely assembling his own team of villains to do his bidding before the huge final battle. Zemo makes a perfect candidate, he tore The Avengers apart as a plain old human and that will not have gone unnoticed by Thanos.
We know the MCU likes to take liberties with original comic storylines, so there's nothing to stop Zemo discovering Adhesive X through Thanos and we welcome the true Baron Zemo to the MCU.
We won't see much of the Avengers during the next few years before Infinity Wars - Stark will be popping up in Spider-Man Homecoming and we have Ant-Man, which at most will be referencing Scott Lang's current fugitive status after Cap broke everyone out of The Raft - we're going to have assume that The Avengers are still fractured and reeling from the results of Civil War but we know IW2 will require the Avengers coming together with other heroes, so what's going to reunite them?
Sadly, this could be the long rumoured death of Steve Rodgers.
We assumed this would happen in Civil War, but with an Adhesive X covered Baron Zemo working for Thanos, it's entirely likely that Steve is going to face Zemo for one last time. Having killed Bucky in the comic books, the MCU could flip that on its head and Zemo will kill Steve in IW1, a catalyst for the remaining Avengers to set aside differences to avenge Steve's death and after battling Baron Zemo, find out the Thanos connection. But this will not be the end of Baron Zemo.
Post Infinity Wars we're left to grieve over the death of Steve and a vacancy at Captain. Given the remaining movies on Sebastian Stan's contract, assuming he is in both Infinity War features, we have room for a trilogy in which Bucky is determined to catch Baron Zemo and truly make him pay for the death of Steve Rodgers. We may even see Clark Gregg finally reprising his role as Agent Coulson in the MCU depending on what happens in Agents of SHIELD, because you know Phil is going to want to play a part in capturing the villain who killed his hero.
Now obviously there is still scope for Sam Wilson to take up the helm, but when you take into the screen time of Bucky with the shield, the likely vibranium update to his arm and the strongest personal connection to Steve out of the team, we should expect a discussion between some Avengers on who should take Steve's place, leading to the agreement that Bucky would be best suited (with considerable disagreement from certain Avengers which would make for some heated dialogue).