Citing sources familiar with the matter, Mark Gurman for 9to5Mac reports that Apple is working on iTunes 11 with support for iOS 6 and improved iCloud integration. Gurman says that development of iTunes 11 began prior to the public release of iTunes 10.6, and is largely focused on back-end improvements rather than cosmetic changes to the user interface.
The internal build of iTunes 11 works more closely with iCloud, including the addition of a dedicated iCloud settings panel that allows for users to control their iCloud features such as iTunes in the Cloud, iTunes Match, iOS device backups, and more. Gurman also suggests that, despite development of iTunes 11, Apple might release a minor update to iTunes 10.x for iOS 6 compatibility.
A few months ago, 9to5Mac reported that Apple is working on revamping its iTunes and App Store platforms for release later this year.