Going by Paul Thurott, we'll see the Xbox 360 Mini and obviously an overall price drop. I honestly don't expect much more, the heat is on for Microsoft to impress with the Xbox One, so I see them wrapping that up in five to ten minutes tops. After that, it's moving swiftly on to the absolutely stupid amounts of games they have coming.
Compare to Sony who will need to give at least equal time to the VITA and have a not inconsiderable amount of entertainment, services, functionality and design they still have to talk about.
Still 90 minutes just won't be enough, so there should be many announcements (read: megatons) saved for Gamescon and TGS IMO.