User blog comment:Kogath/Monster Hunter X Discussion/@comment-6050823-20150901223601/@comment-5167887-20150903025238

^ Also we have no clue about the timeline of this game, whether it happens before or after 4U.

Since it's not a numbered title, it's likely to be a sort of "MH paraverse" where every timelines are mixed up in some way. There still are possibilities of Seregios and Magala sightings. Look, the Lagia from X is "more evolved" than the one of 3U.