There have been several nods to the X-Men in the MCU since Disney acquired the rights back in 2019. From cameos in The Marvels and Doctor Strange and the Multiverse of Madness to Wolverine's entry in Deadpool & Wolverine,

Forget the Red Hulk – Captain America: Brave New World ‘s real “big debut” is adamantium. After all, adamantium’s introduction in the upcoming blockbuster is surely a signal that the MCU’s new Wolverine – and by extension, the franchise’s long-awaited X-Men reboot – is edging closer to the big screen.

That's because Captain America: Brave New World brings adamantium into the fold. The substance shows up in the body of the Celestial that emerged from the Indian Ocean in Eternals. Now, it's the cause of international conflict, as major world powers try to control the world's only known adamantium supply.