Quite a few questions remain for the fate of the MCU and how Marvel plans to carry the universe and characters forward after the climactic conclusion of Avengers: Endgame. The climax proved so titanic that much of the status quo was rocked and shaken from its foundation, leaving their founding heroes either lost or changed forever. But one Marvel mainstay was broken long before Endgame, and its name was Mjolnir.
Pulled straight from mythology, Thor's mighty hammer Mjolnir was always a major part of his character and often the source of the plot in his comics and feature films. His debut movie involved a test of his worthiness to wield the hammer, with Thor's father Odin enchanting the weapon with the words "Whosoever holds this hammer, if he be worthy, shall possess the power of Thor."
But as Thor's character grew, the real test became learning to find himself without the hammer. In Ragnarok, Thor's lost sister Hela seized the hammer in her hands and, in a display of jaw-dropping power, shattered it with barely any effort. The moment not only established Hela as a massive threat, but set Thor on a journey of self-discovery that culminated in regaining his powers to become even mightier than ever before. But the tragic casualty of the moment was Thor's iconic hammer, and it's hard to imagine how the title could pass to his successor without the hammer passing with it.
Jane Foster, portrayed by Natalie Portman, is all set to claim the godly title of Thor for herself in the upcoming Thor: Love and Thunder while Chris Hemsworth's character will appear in the Guardians of the Galaxy sequel. While it is up to Jane to fill the role of the goddess of thunder as ably as she can, it's hard to imagine her doing so without Mjolnir in her hands. But how could Marvel possibly bring the hammer back after it was so irreparably destroyed?
The situation isn't exactly a novel concept in the comics. Mjolnir has been broken and lost and repaired and replaced before, and there is a deep well of examples from the comic world the MCU could draw from for inspiration. Most recently, in a seemingly hopeless battle against the villain Mangog, the Jane Foster of the comics sacrificed Mjolnir in order to win her battle. She bound the villain to the hammer with the unbreakable chain Gleipnir and hurled him into the sun.
All that remained of Mjolnir in that instance was a granular fragment that still possessed its worthiness enchantment, meaning that despite its small size it still proved extremely heavy to those who were unworthy. The original Thor ended up convincing Mother Storm to forge a brand new Mjolnir, and some possible parallels for the options available to the MCU become clear. Not only do fragments of Mjolnir still exist from when Hela shattered it, but the MCU Thor was able to replace his Mjolnir by forging the new weapon Stormbreaker.
It's also notable that Mjolnir was rather easily replaced in Endgame when Thor borrowed an alternate timeline's iteration of the weapon and brought it with him to wield in the final battle. That means there are three perfectly viable options available to Jane: 1.) She can have the fragments of the hammer repaired; 2.) She can replace the hammer with a new weapon, or 3.) She can replace it with an identical counterpart from another timeline. Given that it's such an integral part of the character, it goes without saying that something needs to be done to get a hammer in Jane's hands.
The best bet would be on forging a replacement, given that the comics often serve as a testing ground for possible MCU plots. With the hammer most recently being replaced in Thor's hands by such a method, it seems like overly convenient timing before the release of Thor: Love and Thunder for that not to be the explanation at hand. Of course, with Doctor Strange and the Multiverse of Madness promising the exploration of other timelines and realities, it would be a pretty simple matter for Jane to get another world's Mjolnir.
In fact, there's no reason the Jane of Thor: Love and Thunder couldn't be an alternate Jane herself. With the possibility and promise of alternate timelines, a world in which Jane first found Mjolnir and wielded its power for herself before coming to the main MCU timeline could offer exciting possibilities, and allow the character to stand on her own as an individual rather than being known simply as "Thor's ex-girlfriend." It would give a chance for Natalie Portman to bring something fresh to the character, something not seen before. There are a few things you can change and some you can't, and while a Thor needs a hammer, Jane Foster proves that a Thor doesn't need to be what we expect.