Avengers: Endgame marked the end of the MCU journey for several main characters, including Tony Stark, Natasha Romanov, and Steve Rogers. However, the end of their journey does not necessarily mean they'll never make an appearance in the Marvel universe again. Natasha Romanov has her own movie set to be released soon, Black Widow, which takes place after the events of Captain America: Civil War, but the others have already had their own films. Does that mean they will never be seen again Earlier this year, Marvel fans were swept up in excitement when a report claimed that Chris Evans was heading towards closing a deal to reprise his role as Captain America in one or two future Marvel projects. These would be smaller or supporting roles rather than headlining a movie. Chris Evans appeared to shut down the rumors on Twitter, tweeting "News to Me" with a shrug emoji.
Fans refused to be deterred, however. It wouldn't be surprising if Chris Evans was denying or misleading audiences with his tweet in order to preserve the surprise of a future appearance. It's also possible he will be making only cameos and did not want fans to expect larger appearances. With the amount of upcoming Marvel TV series and movies, there are tons of projects that could possibly feature cameos from Steve Rogers. Everything suggested below is a theory, as no Captain America cameos have been confirmed.
The Falcon and The Winter Soldier
A Captain America cameo in this upcoming Disney Plus series would be so obvious it almost makes it less likely. The titular characters are two of the characters most associated with Steve in the Marvel universe. The trailers show that the series does not shy away from the shadow of his presence, and both Bucky and Sam wield the shield during the trailers. There has also been a brief clip in multiple trailers of U.S. Agent, the government-sanctioned successor to Captain America, who could definitely cause a lot of tension and strife in the series.
One of the more obvious ways Steve could make a cameo in The Falcon and The Winter Soldier is through flashbacks. Flashbacks to either the Avengers era or Bucky's time in the war with Steve could be easy ways to provide a meaningful cameo for Captain America. Another possibility comes through a trope commonly used in media; either Bucky or Sam are trapped in a stressful or traumatic situation alone and hallucinate Steve as a way to work out their issues and escape. This would take up at least one of their full storylines in an episode, and with only six episodes of the show, it's possible there wouldn't be time for a cameo like this to happen in the series.
Fantastic Four
After two different versions of the Fantastic Four team have already come to the screen outside the MCU, Marvel Studios gained the screen rights to the franchise. Marvel confirmed that the Fantastic Four would be introduced into the MCU in their own movie. Kevin Feige announced that the director of Spider-Man: Homecoming, Jon Watts, would be directing the Fantastic Four film.
A Captain America cameo of some sort in the Fantastic Four film would be fun on a metatextual level. Chris Evans famously played Johnny Storm, the Human Torch, in the 2005 film Fantastic Four and its 2007 sequel Fantastic Four: Rise of the Silver Surfer. Him making an appearance in an MCU Fantastic Four would be a fun wink and nod to his previous role. Captain America could make an appearance in a flashback, with one of the characters encountering him in the past. A flashback could also allow for a cameo from the other MCU actor who played the Human Torch, Michael B. Jordan.
Doctor Strange and the Multiverse of Madness
While there isn't a lot of confirmed information about the upcoming Doctor Strange sequel, it is pretty clear that it will be dealing with the multiverse. This opens up a lot of possibilities in terms of showcasing connections within said multiverse, especially regarding properties that were previously not a part of the MCU. However, this could also open up the possibility of bringing back new versions of characters already existing in the MCU, including those who have died in the primary timeline.
Captain America could make an appearance as another version of himself, whether that be an evil version of Steve, a Steve who isn't a super soldier, or just a version of himself that took a different path. This could manifest as a comedic cameo and more of a fun cheeky appearance of the character, or as a serious moment where the characters encounter a version of a friend they lost.
Loki
Another upcoming Disney Plus series, Loki follows a character who himself is dead in the main Avengers timeline. This Loki escaped capture after the events of the first Avengers, as seen during Avengers: Endgame. In this series, Loki is caught by the Time Variance Authority, who monitors the timeline. He can be seen in the trailers in different moments in history and space, and even attempting to travel back to Asgard.
This opens up several possibilities for a cameo by Captain America. A cameo in Loki would likely be on the comedic end. Since Loki is traveling after the events of The Avengers, he could sneak through the background of moments from previous films or moments that happened offscreen, similar to Avengers: Endgame. This would provide an excuse to include cameos from multiple characters, including Captain America. Steve could also make a cameo similar to that in Thor: The Dark World where Loki uses an illusion to make himself look like Captain America.
Other Possibilities
There is a range of minor cameos that Captain America could make in upcoming MCU projects. While not listed in the voice cast for animated series What If...?, Chris Evans could make a surprise appearance during a voiceover or within an episode. The trailer for the show includes clips of Peggy Carter as Captain America and a zombie Captain America, so either of those episodes would be an obvious choice for a cameo appearance.
Captain America notably made cameos in Spider-Man: Homecoming in a series of video PSA's that Peter and his friends watch in school. They watch one during gym class and one during detention, while another airs as a post-credits scene. This could become an entertaining running gag for other MCU projects with scenes in high schools or universities. It would be a fun way to keep Captain America in the MCU for a long time.