Originally Posted by
Smaikiii
I have 13 mythic kills (6 last ID + 7 this ID) right now and the new mission rewards Azeroth Invasion Plans - ID 152316 which is the highest ID of the four different plans (LFR/NHC/HC/M).
So I think this should be the mythic version.
EDIT: My warlock alt has ID 152315 and this is definitely heroic.
EDIT 2: A guild mate has only 12 kills and got the heroic cache.
You need 13 kills for the mythic cache!
IIRC, the item you receive is determined as you LOOT the mission, not when you send it off.
For example, you can have the heroic quest item, send the mission off, kill more mythic bosses and reach the magic number 13. If you loot the mission now, you get the mythic quest item.