Predicting the next expansion through the last content patch?

Blizzard's new quicker expansion development model involves using many assets from the latest content patch of an expansion as the central launch theme of the next expansion. Siege of Orgrimmar had a lot of 'Iron Horde' models and such from armor to small and large decorations (the Iron Spiked Ball thing, whatever it's called), and a lot of the Siege of Orgrimmar armor models and decorations were re-used in the Draenor zones for the Iron Horde and Blackrock Foundry.
Similary, the Hellfire Citadel content patch came with a lot of demon model updates and even a few new demons and other decoration models which I'm now seeing being used plenty in certain zones and class halls in Legion.

I didn't find the right solution from the Internet.

References:
http://www.mmo-champion.com/threads/1915...t-content-patch

Engineering Process Video Example