Doctor Strange 2: 5 Ways The Character Can Return For The Sequel
1. Thanos Needs Help
In the Infinity War comic arc, after Thanos has battled The Avengers, there is the emergence of another cosmic being possibly even greater than The Mad Titan himself, forcing him to temporarily team up with Earth's Mightiest Heroes.
Adjusting for the difference in Thanos' motive between the comic and the movie, this new villain would threaten to destroy the universe that the adoptive father of Gamora has sacrificed so much to save, possibly taking advantage of the fact that half universe has been destroyed.
Reluctantly, seeing no other alternative, the hurt Titan would have no choice but to fight on the side of the good guys as a means to an end, but would surely be smart enough to see that they would stand a much better chance of victory with Doctor Strange on their side.
This may lead Thanos to bringing back Strange, and possibly a handful of others, in order to defeat this new threat, whether it is a previous MCU villain like Dormammu, a potential new MCU villain like Galactus, or if Marvel stay true to the comics, The Magus.