I mean there was alot of crazy ideas that I heard on the Meeting Of A Thousand Suns documentary. They a few songs that sounded more like jam seshs but were really good (Chester singing agressively and Rob drumming, harmonica/piano, and more). There was also two demos that were in their top few favorite songs. One was a da-na-na-na song which I really liked, and the other had a really dark and ambient beat.
They have to give us something. Maybe they didn't want to release anything right after the album came out because people would try to piece it in the story, or maybe they didn't want people screaming "th1s shoooood replaces the eMpty spacesss yo". Who knows.