A new theory from a Marvel Studios fan on the Reddit states that the Fantastic Four may get introduced soon and it will be closely related to the Quantum Realm.
The Quantum Realm is a subatomic world where Janet Van Dyne was trapped in the 80’s. She ultimately got rescued by Hank Pym, the new Wasp Hope and Ant-Man Scott Lang during the events of Ant-Man and the Wasp.
Having spent a lot of time in the realm, Janet emerged with a lot of new abilities that allowed her to neutralise Ghost’s condition of being stuck in a constant flux. Here lies the key to this theory.
The user suggests that like Janet, Reed Richards, Johnny Storm, Sue Storm, Ben Grimm and maybe Victor von Doom will travel to the Quantum realm and emerge with their new powers.
“Okay, so we know that the quantum realm can change people’s biology, like how it changed Janet after staying in the quantum realm for so long, my idea is that Reed Richards doesn’t take Susan, Johnny, Ben (and maybe even Doom) to space, he takes them on a trip to the quantum realm, where a mishap with their ship or equipment cause them to have to abort their mission and try to leave the quantum realm in a hurry where the ship or something explodes, causing a wave of devastating quantum energy to hit them, I’m not exactly sure how each of them get their powers but stay with me here- Johnny could be the mechanic of the team and is closest to the engine room where the explosion happens, giving him is fire powers.” the Redditor writes.
This is pretty similar to the 2015’s Fantastic Four reboot where they travel to the Negative Zone. Even Doom was the part of the group at that time, eventually becoming the greatest foe for the team.
The user also suggests that the circumstances shown in the film might explain why each member gets their own unique set of powers. However, it’s safe to assume that the Quantum Realm will have a major role to play in the future of MCU, most likely in next year’s Avengers 4.