Discover what? You find a full completed raid in game, then I'll believe that they held out. All you have is terrain which is there to streamline development in the future. If they waited until everyone was ready at the same time then you'd have ONLY the terrain/landscape teams working. You can't add enemies or balance content that has nowhere to go. Do you think waves of enemies in a strike are an arbitrary number? No, everything down to the number and type of enemies is calculated for difficulty. If you don't know what a huge room looks like or what hallways and doors it has you can't even begin to do that. This super secret locked away conspiracy content is normal and there so we get content FASTER, not to keep it from us!