Obviously INFINITY WAR is gonna break records. The only way they can top its success is if they incorporate Jackman's Wolverine and Reynolds' Deadpool in the second part. Just have Doctor Strange explain Thanos wielding the Gauntlet is causing a rift across the multiverse so he brings them in to help out the gang. Feige's even said the IW films will cause a major shakeup, essentially hitting the soft reset button for phase 4. Why not let them be a celebration of Marvel on film since 2000?
Once everything is settled and back to normal at the end, they can retire that universe if they want to and introduce mutants into the proper MCU as their own thing. Boom. AVENGERS 4 makes all the money in the world, and Marvel still has the freedom to reinvent the characters however they want. New Wolverine, no ties to the Singerverse, etc.
