Marvel Studio is very tight lipped about their plots for the movie and the fact that each film in the Marvel Cinematic Universe being linked to each other in their plot, we never know how the film will ultimately shape up.
It is being said that Chris Hemsworth’s contract with Marvel has only one film remaining, apart from Thor 3. This means that we might not see him again for another Thor movie. The next film in the Phase 3 of the Marvel Cinematic Universe Captain America: Civil War and Avengers: Age of Ultron is expected to be Avengers Infinity War Part 1 and Part 2, which will be shot back to back.
Marvel is planning on focusing on other superheroes like Ant-Man, Black Panther, Doctor Strange, Captain Marvel, after Infinity Wars that will end the Avengers.
Phase 3 of Marvel Cinematic Universe already has quite a few lined up, and all of them will impact the final plot of Thor 3: Ragnarok. Thor 3 is expected to release in the November of 2017.