User blog comment:Kogath/Monster Hunter X Discussion/@comment-28303251-20150810070231/@comment-2194133-20150811193306

It is only logical for Zinogre to get a Rare. Think about it, most Rare Species (not counting Gold Rathian) in the main games are flagships who were also given subs:

Rathalos (MH or MH Freedom flagship) > Azure Rathalos > Silver Rathalos

Tigrex (MH Freedom 2 flagship) > Brute Tigrex > Molten Tigrex

Nargacuga (MH Freedom Unite flagship) > Green Nargacuga > Lucent Nargacuga

Lagiacrus(MH3 (~tri) flagship) > Ivory Lagiacrus > Abyssal Lagiacrus

Therefore Zinogre (MHP3rd flagship), who has Stygian Zinogre as a subspecies should be next in line.

Flagships with present variants like Brachydios or Gore Magala are a different case so I wouldn't expect Rares from them anytime soon, same applies to Seregios who does not yet even have a sub.