User blog comment:Kogath/Monster Hunter: World Discussion/@comment-26421638-20180704154711/@comment-5158920-20180704155245

Taking a wild guess here with Behemoth releasing in August. Oroshi= October, Alatreon= December. Could swap Oroshi and Alatreon around or they might arrive earlier or later. I'm just guessing random dates for new additions is all. They could give us the other Elder's as Arch-Tempered versions between those months I mentioned.