For the most part, the Doctor Strange movie was a self-contained installment of the Marvel Cinematic Universe. But after the main story had concluded, Stephen Strange branched out into the wider, non-magical MCU when he met with Thor at the Sanctum Sanctorum.The Doctor Strange mid-credits scene showed Strange promising to help the God of Thunder find Odin, and it was later confirmed that the Master of the Mystic Arts would appear in Thor: Ragnarok. Thanks to a Japanese trailer for the third Thor movie, we have our first taste of how Doctor Strange will fit into the narrative, and it involves him delivering cryptic advice to Thor Odinson.
Most of this new Thor: Ragnarok trailer (posted by Cinema Today) plays similarly to the one that was screened at San Diego Comic-Con last month, but the beginning of the preview shows Doctor Strange and Thor back in the Sanctum Sanctorum. This scene appears to take place directly after their conversation in the Doctor Strange mid-credits scene, meaning they're about to go looking for Odin. But before the search begins, Strange tells Thor that he senses a great change in his future, and that destiny has dire plans for him. Thor isn't particularly fazed by these words, responding that he has dire plans for destiny. From there, the trailer delves into the main story Thor: Ragnarok story points, i.e. battling Hela, getting into trouble on Sakaar, etc.
It's hard to tell what Doctor Strange is specifically referring to when talking with Thor in this new trailer. If we're looking purely through the Thor: Ragnarok lens, then the "great change" could refer to Thor losing his trusty hammer, and destiny's "dire plans" is connected to Hela, the Asgardian goddess of death, trying to destroy Asgard with the apocalyptic Ragnarok event. However, with Avengers: Infinity War on the horizon, perhaps Strange is vaguely aware of the events to come (either through his magic or the Time Stone) when Thanos and the Black Order arrive on Earth, and that epic tale will show Thor being dealt an unexpected blow.
Although Doctor Strange is showing up in Thor: Ragnarok, he's not expected to play a major role in the story. One could surmise that after he locates Odin for Thor, Strange will return to the Sanctum Sanctorum to continue his sorcerous duties. It also appear that his involvement may just be limited to the beginning of the movie since most of Thor: Ragnarok's action will take place away from Earth. Fortunately for Thor, even without Doctor Strange accompanying him across the Nine Realms, he won't be lacking for superhero assistance. That's because Thor will reunite with Bruce Banner, a.k.a. The Hulk, on Sakaar, and they'll later join forces with Valkyrie and Loki to stop Hela and her allies from unleashing Ragnarok.
Thor: Ragnarok arrives in theaters on November 3, and both Thor and Doctor Strange will return on May 4, 2018 for Avengers: Infinity War.