Most people don’t like to talk about Thor: The Dark World. But it is an extremely important film for the story of the MCU, and it certainly showed us a lot of references for the future of the MCU. That is why even Endgame went back to Thor 2 through Time Travel. It referenced the MCU as Universe 616, it foreshadowed Thanos’ Snap using Schrodinger’s cat as a reference, and there were so many other references to the Marvel Multiverse. All these actually came from Erik Selvig’s chalkboard that was shown right when Stan Lee made his cameo. And on this board, one such Easter Egg was of the X-Men, found by Screen Rant.
The MCU Phases 4 & 5 will certainly build up towards the establishment of the X-Men. But for now, let’s discuss the X-Men Easter Egg written on Erik Selvig’s chalkboard illustration – ‘The Fault’. This in the comics was an event created by a devastating war between the Shi’ar and the Kree. A galactic war was triggered by the powerful Omega mutant named Vulcan who had conquered Shi’ar. In the final battle between the Shi’ar and the Kree, the Kree detonated a device called the T-Bomb while Vulcan was fighting Black Bolt. This bomb tore a hole in the fabric of space & time and created The Fault. This tear in reality further created the Cancerverse, which is still playing a role in the X-Men comics.
The Cancerverse has become the breeding ground for the Alien race called The Brood, who are rumored to be the villains of the upcoming Captain Marvel sequel. So, perhaps the Fault could happen in the MCU, but we don’t know whether it’d be exactly same as the comics. We’ll have to wait and see whether any Phase 4 project leads up to it (WandaVision certainly could).