Doctor Strange has begun to open internationally, and like most Marvel films there are two post-credits stingers.
The first is the one in the middle of the credits after the flashy cast credits.
In a scene directed by Thor: Ragnarok director Taika Waititi you see Thor arriving at the Sanctum Sacntorum and talking with Doctor Strange. The Sorcerer Supreme offers Thor a drink and says he will help him track down where Odin is, but in exchange he and Loki return to Asgard and never return to Earth.
After the rest of the credits is a smaller stinger where Baron Mordo begins to take on the villainous persona he’s known for in the comics. With another major Doctor Strange villain making an appearance in the movie, and with Mordo turning heel, there’s definitely enough setup here for a series of Doctor Strange movies.