An article from Bloomberg today speculates that with Ballmer leaving, there's a very real possibility that Microsoft will spin off the Xbox division sooner rather than later.
PC Magazine columnist John C. Dvorak is a proponent of busting Microsoft into four to six entities, and believes this is a good start. "Some analysts see the proposed Xbox Corporation being valued around $17 billion right out of the chute."
"When you really think about it, the Xbox is unlike anything else Microsoft does. The company stuck with this product and developed a winner by actually being patient for a change. But still, the profit margins are not there insofar as Microsoft is concerned and it might just be spun off to make the books look better."