User blog comment:Kogath/Monster Hunter: World Discussion/@comment-25083735-20190604201317/@comment-184612-20190604214500

Alatreon has never been teased and Fatalis was just used for the 15th anniversary. It's also highly doubtful that Velkhana is the final boss since it's been shown so early. It probably just has a role similar to Nergigante.

Glavenus is the true flagship for Gen, so I doubt we'll see the other three show up.