According to an article about Apple's Eddy Cue in the Wall Street Journal, iTunes 11 is imminent, and may even be released today. The report says that the new version of this desktop software will have greater integration with iCloud, the principal benefit being that you don't have to download all of your music and movies to whatever device you're using. Your media will be ready and waiting in iCloud whenever you want to access it. The new version more closely resembles the mobile version in that regard.
According to the WSJ, iTunes 11 will allow you to stream music, movies and TV shows that you've purchased on any of your devices — no need to sync and download again. Purchase on one device once, and your media is then available to all your devices. You'll still need to purchase and download the file to one of your devices the first time, but then it will be available to all.
The Journal says that Apple is feeling pressure from competing services such as Pandora and Spotify, which let you subscribe to their service and then stream music without first purchasing individual songs.
This seems like a good move. The cloud is the future. There have also been rumors that Apple itself will offer a streaming music service similar to Spotify.