GMS v138 - Xenon

Not necessarily. It could also come from the new Magic Harps since that's where the Sovereign gear comes from. Perhaps when you hit "Fever", the rewards change to Sengoku gear and the new Terminus weapons.

Considering that they have already given us a rough list of what equip sets are available from it, I seriously doubt that Terminus weapons would be ninja'd in there. If they were in there, they would say. They would obviously get more sales if they were.

EDIT: Ninja'd!