Warning: This Article Contains Spoilers!
Thor 3 actually follows the format of The Avengers and Guardians of the Galaxy by giving us one mid-credits scene that acts as an important button for the next chapter of the MCU saga, as well as a post-credits scene that is strictly for laughs.
Here's the breakdown of what Thor: Ragnarok's mid-credits and post-credits are all about:
The mid-credits scene of Thor: Ragnarok sees Thor, Hulk, Valkyrie, Loki, and all the surviving Asgardians on a journey through space aboard a large spaceship. The group is searching for a site upon which to establish a new Asgard; Thor is in the middle of reassuring Loki that all will be well, despite their hardships, when suddenly their ship is cornered by a spaceship so big it makes their lifeboat look like a child's toy.
Things cut to black with Thor and Loki still looking out the window at this ominous new development, leaving Marvel fans guessing about what's about to happen.
It's not hard to infer what the scene is setting up: It seems that Thanos (or his forces) have finally caught up with Loki, who is implied to have stolen the Tesseract from Odin's vault, during Thor's climatic battle with Hela. With Loki and The Tesseract now in his grasp, Thanos has the first pieces to the puzzle he needs to assemble in order to activating the all-powerful Infinity Gauntlet. The mid-credits scene also implies how Thor winds up crashing into the windshield of the Guardians of the Galaxy's Milano, a moment teased in the Avengers: Infinty War Comic-Con trailer.
The post-credits scene of Thor: Ragnarok gives us a final look at how Jeff Goldblum's Grandmaster is faring, in the aftermath of the movie's events. It's a little irreverent bit of comedy to end on, and is in keeping with family tradition, as Guardians of the Galaxy's post-credits scene featured a similar moment with The Grandmaster's brother, The Collector (Benicio Del Toro).
In the scene, Goldblum gets to ham it up one last time, as The Grandmaster emerges from some kind of escape pod / panic room with two of his consorts, he finds the savage citizens of Sakaar waiting for him, with guns drawn.
The Grandmaster immediately starts pontificating about how great it is to see a social revolution happening on Sakaar, and credits his own role in making it happen (can't have a revolution without someone to overthrow). It's left uncertain whether Grandmaster can turn the crowd to his side, but given how disgruntled his formerly oppressed subjects are, it doesn't look good.
Thor: Ragnarok is now in theaters. Other upcoming MCU movies include Black Panther on February 16, 2018, 2017, Avengers: Infinity War on May 4, 2018, Ant-Man and the Wasp on July 6, 2018, Captain Marvel on March 8, 2019, the fourth Avengers movie on May 3, 2019, the sequel to Spider-Man: Homecoming on July 5, 2019, and Guardians of the Galaxy Vol. 3 in 2020.