"Hey Siri" support and possibly wireless charging case alongside AirPower charging mat.
Next Version of iTunes Restores Local Contact and Calendar Syncing
According to the release notes, iTunes 11.1.6 "restores the ability to sync contacts and calendar information to your iPhone, iPad, or iPod touch from your Mac running OS X 10.9.3."
When iOS 7 and Mavericks were introduced back in September, Apple removed local syncing in favor of cloud syncing, allowing users to sync calendars, contacts, bookmarks, and notes only via iCloud. Many users were unhappy with the feature removal and their inability to sync information to their iOS devices using their Macs.
Apple's Support Communities has a 212 page thread on the issue, and MacRumors has received multiple complaints about the removal of local sync since Mavericks was released. It appears that the next version of Mavericks and iTunes 11.1.6 will restore the feature, once again allowing users to sync locally.
At the current point in time, iTunes 11.16 and the newest version of OS X 10.9.3 are only available to Apple employees, but the betas should be seeded to developers in the near future.