I'm not sure about totally new document format. But I would like to see something new in file collaboration. A system that is distributed, and standardized (a new protocol for file collaboration, something like http but for binary blobs, p2p is a nice start but something that works better for enterprise collaboration).

Cloud services in this space are nice but they are all centrally managed. And collaboration between different centralized systems doesn't work (say between SharePoint, and Google Drive).