According to a tweet from him Cullen Bunn has no upcoming work on X-books after he finishes current work. https://www.bleedingcool.com/2018/09...-to-the-x-men/
I liked his Magneto series and alot of what he did with Erick. His Uncanny run was good and i thought he did a good job of bringing in some old themes and characters updated to fit the Mist era during the X-men. Was a staple linchpin to the franchise during difficult times. I believe his work on blue maybe remembered as a important part to his contribution to the X-men, because he helped bring the 05 to the current X-fans.