Sprint recently sweetened their offer for Clearwire and it was apparently enough to push Dish away. Dish has announced that they have withdrawn their offer to acquire Clearwire, citing a "change in recommendation" at Clearwire. In plain English, this means that shareholders now prefer Sprint's sweetened offer and are suggesting the board take it instead of Dish's.
Interestingly enough, Sprint is about to be acquired by Softbank as soon as it clears all of the regulatory hurdles. In other words, Softbank will be acquiring Clearwire and the spectrum that Clearwire owns. It's not clear what Sprint plans to do with Clearwire after the acquisition, though they'll likely make use of the spectrum for faster LTE.