Natalie Portman's Jane Foster is returning to the MCU in Chris Hemsworth and Tessa Thompson returning as the God of Thunder and Valkyrie, King of Asgard.
Thor 4 will also see Jane Foster's Thor should be referred to as the Mighty Thor. The name has a rich history behind it; Stan Lee always tended to use adjectives to describe his favorite superheroes, and The Mighty Thor was his favorite way of referring to the God of Thunder. It was used on the cover of 1962's Journey Into Mystery #83, Thor's debut issue, and has stuck ever since.
It's a fitting adjective for Thor, not least because it perfectly describes the kind of character Lee wanted to create in the first place. Fresh from the success of the Hulk, Lee was trying to think of a character who could rival the Jade Giant in strength, but who could also embrace the more fantastical side of the comic book genre. As Lee noted to his biographer George Mair, "How do you make someone stronger than the strongest person? It finally came to me: Don't make him human - make him a god." The term was associated with Thor up until 2004, when Marvel ended the Mighty Thor run due to poor sales performance.
In 2007, Marvel Comics relaunched the Thor franchise under writer J. Michael Straczynski. In order to differentiate it from previous runs, they dropped the "Mighty" adjective and simply called the book Thor. The Straczynski run is a major source of inspiration for the MCU's version of Thor - the popular scene in Thor showing crowds trying to pick up Mjolnir is lifted straight from it. As a result, while Thor has occasionally declared himself "mighty," the adjective has generally been avoided in the films.
Fast-forward to 2014, when writer Jason Aaron unveiled the Mjolnir's power in ways even the Odinson had not.
Marvel Studios now faces a similar issue to the one Jason Aaron encountered back in 2014. They need to be able to differentiate between Thor Odinson and Jane Foster's Thor, and like Aaron they don't just want gender to be the key factor. Given that's the case, it makes sense for Marvel to follow the comics' lead and use the adjective "Mighty" - particularly, because, on the big screen, that word hasn't been used with reference to the Odinson quite so many times. It will be interesting to see whether or not the MCU's Jane Foster proves herself mighty in the same way as the comic book character did, and uses Mjolnir in ways that left even Thor Odinson envious.
