Sources who declined to be named because they are forbidden to talk publicly about Apple’s plans tell AllThingsD that the company has been “borrowing” engineers from the OS X 10.9 team as part of an effort to double down on iOS 7. “Yes, yes — it’s essentially a repeat of the iPhone/Leopard scenario,” one source said, referring to Apple’s 2007 decision to pull engineers from OS X 10.5 to work on iPhone. “Not as much of a fire drill, though. It will ship on time.”
Dalrymple confirms by simply stating, "Yep."
AllThingsD's report follows an earlier one from Bloomberg which basically said the same. Apple is expected to be altering the user interface of iOS to remove the flashy, skeuomorphic design in favor of a more flat design. Of course, it will likely be unveiled at WWDC.