How would they know to drop a swamp key if they had not yet designed the swamp around locked crypts? How would they know to design an ore-finder if they had not yet designed the mountains with hidden ore pockets? This is what you are asking. Personally I think they should by now have a concept for the remaining content, eg maybe the ashlands has a fire extinguisher item from the boss or whatever the gimmick will be .. but if they haven't gotten to that point, a placeholder is fine.