This is a rather quick filming schedule, but is actually only slightly longer than Deadpool‘s.
However, Pierce Brosnan and Russell Crowe have been linked to Cable recently, while Kerry Washington is a favorite for Domino.
Producer Simon Kinberg recently confirmed that Fox intends to have Deadpool 2 be a 2018 release, with their previously established March date the prime landing spot.
This new filming schedule and proposed release would still leave Fox six months for post-production work, which should be more than enough considering that the sequel is aiming to be on a similar scale to the original.