Preview at WWDC likely in June, followed by September launch.
Apple Continues iTunes Match Developer Testing with iTunes 10.5.1 Beta
With Apple having pushed iTunes 10.5 out to the public earlier today, the company has already seeded developers with a beta version of iTunes 10.5.1 to continue testing of its forthcoming iTunes Match service.
iTunes 10.5.1 beta 1 includes several performance enhancements and bug fixes, and is a required update for all subscribers to iTunes Match beta. iTunes Match is not included in the iTunes 10.5 GM release.As with previous builds testing iTunes Match, Apple notes that iCloud libraries will be deleted at the end of the beta testing period.
iTunes Match was initially part of iTunes 10.5 and appeared set to debut alongside iOS 5 and iCloud, but at Apple's media event last week the company announced that iTunes Match would not launch until the end of October. The last beta version of iTunes 10.5 still had some remaining issues with iTunes Match functionality, and Apple has given itself a few more weeks to address those problems by pulling the feature out into a separate iTunes 10.5.1 release.
iTunes Match is a $24.99/year service that allows users to have their music libraries matched to Apple's database of over 20 million tracks, making those songs available for use on any iCloud-enabled device associated with the user's accounts. Songs not available in the iTunes Store can be uploaded to Apple's servers and also made available across devices. iTunes Match will be a U.S.-only feature at first, but Apple is apparently working to extend it to other countries soon after its initial launch.