My theory is that all items marked as dlc=1 in data.xml will be future store items (if not already in store), while dlc>1 will be used for true full dlc content.
Around 2-3 updates ago several new still unreleased dlc=1 items where added in data.xml, while all other dlc=1 items added before that point got released in most recent update as store items.
So I'm expecting same pattern here.
Hint: expect new spell packs, lords and great mages/perks.
Hint2: check achivement list and GM perk editor for additional clues.
Obviously, this is all speculation. There is nothing stopping Paradox from making different business decdion and to do something else with unreleased content.