When Disney officially purchased Twentieth Century Fox to reboot other Marvel properties like X-Men and Fantastic Four, only one character from the Foxverse survived the inevitable House of Mouse "snap" and that is the fourth wall-breaking anti-hero Deadpool played by Ryan Reynolds.
During San Diego Comic-Con 2019, fans eagerly awaited news about Marvel's plans with the character heading into Phase Four but zero announcements about Mr. Pool's involvement in the Marvel Cinematic Universe were made. Now, Reynolds is once again teasing Wade Wilson's arrival in the MCU in a new post. Is he finally appearing in Phase 5? We'll have to wait and see!
It'd be interesting to see how he blends in the current MCU timeline and continuity but we have full faith in Kevin Feige and the men and women of Marvel Studios that they can pull this one off.