'The Falcon and The Winter Soldier' might see a new Captain America in John Walker and he's definitely not Sam Wilson's ally
Steve Rogers (Chris Evans) had a happy ending in 'Avengers: Endgame'. He first picked up the shield in the '40s, faced off Hydra, went under the ice after a battle against the Red Skull, and then awoke in the 21st century. Later on, he assisted S.H.I.E.L.D. in their missions, led the Avengers and finally, decided to live out his life in the past after being an integral part in defeating Thanos (Josh Brolin). Now, the moniker of Captain America and the shield has been passed on to Sam Wilson aka the Falcon (Anthony Mackie). To call Wilson a sidekick would be unfair as the man did more than just help Cap and Co. fend off threats. 'Endgame' saw Rogers pass the baton to Sam, and now we're all set to see him as the new Cap in 'The Falcon and The Winter Soldier'.
However, he isn't the only one with the title. The D23 Expo announced that the show would be introducing the John Walker aka U.S. Agent in the series. Walker has been known to be created by the Government to replace Rogers post the events of 'Endgame'. It's understandable as in all probability, Wilson and Bucky Barnes aka The Winter Soldier (Sebastian Stan) were looked at as criminals and fugitives after 'Civil War' and it looks like they aren't pardoned for it. In the meantime, the world needs a new Cap and Walker fills in the void.
The comics saw him being introduced as a villain named Super-Patriot. He was a counter to Rogers as he was a patriotic villain. He gains superhuman abilities after an encounter with a mysterious character named the Power Broker. Walker would eventually take over as Cap was tasked by the Commission of Superhuman Activities to join the ranks of the West Coast Avengers. The team included the likes of established MCU heroes such as Hawkeye, War Machine, Hank Pym, Scarlet Witch, The Wasp, Vision, and Moon Knight. Walker was seen as a man determined to take over the Cap America mantle. In the comic, 'Captain America #354' he uses a discarded costume of Steve Rogers (the original Captain America), a black outfit with a different alignment of the stars and stripes to differentiate it from Rogers's suit.
For now, we can look at how he factors in the series. There have been whispers of the Dark Avengers being introduced in the MCU and Walker does have a slender connection with them. Should the creators decide to introduce them as part of Baron Zemo's plot to destroy the world, then the theory suggests Walker is definitely a rogue. Further adding to this is his rivalry with Cap, he didn't face-off against Rogers in the MCU, but taking on the Falcon might be a start.
Walker's introduction also adds to the other plotline of the world trying to get used to not having the Avengers around. Post 'Avengers: Endgame', most of the superheroes have gone their separate ways. Tony Stark aka Iron Man and Natasha Romanoff aka Black Widow are dead, Hawkeye and Hulk have seemingly retired and the Guardians are off galaxy-trotting. This means the earth is vulnerable to threats and the powers that be decide to replace the superheroes with new ones.
'The Falcon and The Winter Soldier' will debut on August 2020.