God of War's post-credits scenes set up a fight between Thor and Kratos in God of War: Ragnarok. The God of Thunder, who has largely been popularized by the Marvel Cinematic Universe, appears to be taking a more antagonistic role in the sequel as he angrily confronts Kratos and Atreus in that post-credits scene.
The tagline "Ragnarok is coming" suggests that the downfall of the Norse gods is imminent. If Kratos is going to fight, and possibly kill Thor, then it would only be fitting that Kratos wields and fights the other Norse gods with Mjolnir, Thor's signature hammer.
To be clear, Mjolnir isn't an invention of Marvel Comics. The weapon's history has roots in real-world Norse mythology. It's almost always associated with Thor and is the main weapon he uses while fighting. He also uses it to channel and control thunder and lightning. Many people have seen the weapon in action for themselves in the Thor movies until it was destroyed in Thor: Ragnarok.
In God of War, Kratos wielded the Leviathan Axe. And Kratos' axe had plenty of similarities to how people would expect Mjolnir to work in a video game, mainly in that Kratos could throw the axe and summon it back at will.
It's one of the most satisfying video game weapons of all time, and it'd be exciting to see what the same combat designers could do with Mjolnir. There's a precedent of how it could work in other games too.
Thor uses Mjolnir in Marvel's Avengers, and its functions are actually quite similar to the axe in God of War. That shows how good of a fit God of War's combat design is for this weapon. In God of War: Ragnarok, Mjolnir wouldn't even function all that differently from Leviathan. It would essentially just have some flashy lighting-based effects and abilities to distinguish it from the axe's icy magic. It would also be smaller, heavier, and fly straighter — but that's all nuances of digital effects.
It'd also make for an exciting story moment. Imagine a badass scene where Thor doesn't believe Kratos can use the hammer, but he's ultimately worthy enough to pick it up and wield it against Thor himself. A moment like this could capture that same exhilarating rush as when Captain America wielded the hammer in Avengers Endgame.
Just as Kratos' classic Blades of Chaos were a surprising late-game addition in 2018's God of War, Mjolnir could be added to the game partway through as an alternative weapon option. If Sony Santa Monica wants to go even more satisfying and over the top, the developers could give players the badass feeling of dual-wielding both Mjolnir and the Leviathan axe.
Adding this weapon to God of War: Ragnarok would not only lend itself to a cool story moment but add more combat variation as well. With Mjolnir being as iconic as it is and God of War's combat already being a good fit for it, letting Kratos use this weapon in God of War: Ragnarok is a no-brainer.
God of War: Ragnarok will be released for PS5 in 2021.