Apple has been recently busy with new beta versions of iOS 8, OS X Yosemite but the iTunes team has been focused on bringing an "elegant new design" and support for the Family Sharing feature introduced at WWDC. AppleInsider has more details regarding the revamped design that is coming to iTunes 12:
Besides the redesign, Apple's Family Sharing program that allows up to six family members to share content from the iTunes Store is now available, as well. However, you need to keep in mind that each family member must use the same credit card. iTunes 12 also comes with an improved playlist and a redesigned Get Info window.
What needs to be pointed out is that the iTunes Store itself has yet to be refreshed and this will probably take place once iTunes 12 is ready to exist its beta state. At the moment, only developers running a preview build of OS X Yosemite can download the iTunes 12 beta as an update in the Mac App Store.