Chris Evans is set to return as Captain America in a future MCU movie or show, but just how could this happen after Steve Rogers' sendoff in Avengers: Endgame? On January 14, 2021, it was reported that Evans was in talks to return as Captain America, although at the time of writing any further details about how or when are being kept under wraps. While anything right now is speculative, there are a few different ways for Captain America's come back to happen
Having started his MCU journey back in 2011's Captain America: The First Avenger, Evans' time in the MCU came to an end with 2019's Avengers: Endgame. Having defeated Thanos, Steve went back through time, returning each Infinity Stone to its rightful place in order to put the close the timelines created by removing them. Rather than simply come back to the present, however, he decided to stay in the past, finally getting his dance with Peggy Carter, before returning as an old Steve Rogers to give Sam Wilson, aka Falcon, his shield. Whether Steve married Peggy in the main MCU timeline or one of the branched realities created in Endgame remains a point of debate (even between the film's directors and writers), but either way there are options on the table for Marvel.
Marvel could build on the ending to Avengers: Endgame and bring back old Steve Rogers yet again. Since that showed Cap clearly isn't dead in what was then the present of the MCU (which the upcoming Phase 4 movies and shows aren't too-far-removed from), then it wouldn't be a stretch to have him appear again. Phase 4 is shaping up to be a battle for Captain America's legacy, with the U.S. Government having its own opinion on who will be the new Captain America (and clearly not choosing Falcon, at least immediately). A return in The Falcon and the Winter Solider, or another Marvel movie/show with those characters, would work, as Evans could cameo as old Steve to provide guidance to Sam as he struggles to take on the mantle, without totally overshadowing everything or it being a case of the "real" Cap being back.
Chris Evans in Avengers Endgame as Captain America
Of course, there are limitations to what Marvel can do with old Steve, and it would likely limit how much audiences would see of Captain America in the future. If there's something bigger on the horizon, then it would make more sense to have a younger version of Cap appear, with Evans simply appearing as he does now, rather than needing any heavy prosthetics work. Phase 4 offers further narrative possibilities for this: Black Widow takes place in between Captain America: Civil War and Avengers: Infinity War, and Marvel has already done a "prequel" of sorts with Captain Marvel, which took place in the 1990s. There's a clear precedent, then, for more new movies to fill in different points of the timeline, and with Cap's past re-written so he wasn't frozen in ice, then there are a lot of options in terms of when to place a movie or show. One popular option, for example, is a Howling Commandos movie, which could have Evans return.
Then there are the alternate timelines, which will continue to be explored in Phase 4. Several upcoming movies and shows will feature the multiverse, and Loki will definitely be set in one of Endgame's branched realities. It's possible, then, that Evans' Captain America could return in a similar fashion, through an alternate universe or timeline, especially going with the Russos' argument that his life with Peggy takes place in a separate one. With much of the MCU's future seemingly devoted to this line of storytelling, then there'd be plenty of scope for Evans to cameo or even have a bigger appearance somewhere amidst the multiverse. This could be as the same Captain America who went back in time, but it could also introduce a whole new version - for instance, the HYDRA version of Cap from Marvel Comics could be brought into play - because they can go in just about any direction now.
There is also yet another option that Captain America can return by building on Avengers: Endgame's ending, and indeed its time travel, which is having him come back because of Kang the Conqueror. Kang is theorized to be the villain of The Avengers 5 (after he first appears in Ant-Man 3), and as a time travelling bad guy and a major threat, he'll not only require the full might of the MCU to stop him, but could even fight heroes at different points. That means while he could battle some heroes in the present of the MCU, he could go father back, facing Captain America at another point, almost like a reversal of Endgame's time heist. Of course, Chris Evans' return isn't yet official, but if it does happen, there are lots of ways for it to do so.