The Marvel Cinematic Universe has become a big place over the last eight years, so much so that when a new superhero is introduced, it's usually guaranteed that they'll be seen again. That seems to be the case for Doctor Strange, whose movie will officially introduce the MCU to magic in a few months. It's been recently reported that Stephen Strange could cameo next year in Thor: Ragnarok, and now Benedict Cumberbatch is also fairly certain he'll return the year after for Avengers: Infinity War.
While chatting with Empire (via Express) during a Doctor Strange set visit, Benedict Cumberbatch brought up the difficulty of "aligning his schedule with those of Robert Downey Jr, Chris Hemsworth, Elizabeth Olsen and Paul Bettany." While the actor technically didn't name Avengers: Infinity War, that is the only upcoming project where all four of these actors are appearing together. He continued:
To get us all together will be quite something. That's why this character is being introduced, to open up the next chapter. So watch this space to see how that unfolds.
Doctor Strange is one of the prominent players in the Marvel universe, and since he (along with Black Panther and Captain Marvel) is one of the new main superheroes who is debuting in Phase Three, fitting him into Avengers: Infinity War would be a wise decision. However, since Doctor Strange isn't a member of the Avengers yet, it remains to be seen just how big his role would be. Maybe he'll have a prominent presence, or maybe it will be another cameo/minor appearance, and he'll potentially play a bigger part in Avengers 4. As usual, we'll need to wait for Marvel to officially announce if Benedict Cumberbatch will appear Avengers: Infinity War and subsequently fill in the blanks of how he'll be involved, though we do have a few ideas regarding the latter.
Aside from his magical talents making him a useful ally to Earth's Mightiest Heroes, there's also a possibility Doctor Strange has something Thanos wants. One of the artifacts that the Master of the Mystic Arts will wield in Doctor Strange is the Eye of Agamotto, which allows him to manipulate probabilities, or as Kevin Feige put it, "screw around with time." This has led to speculation that the Eye could actually be the Time Stone, one of the two Infinity Stones not yet introduced in the MCU. If that's the case, then Thanos will be paying him a visit to snatch that Eye away from him. Okay, an alien warlord threatening to lay waste to Earth is probably enough incentive for Doctor Strange to get involved in something not directly magic-related, but if the Mad Titan steals one of his sources of power, that provides extra incentive to jump into action.
Doctor Strange will work its magic in theaters on November 4, and Avengers: Infinity War will be released on May 4, 2018.