Apple has filed a patent , that describes an interface for manipulating "three-dimensional virtual objects" on a touch screen. The technology may be used in future releases of iPhone or in the rumoured Apple tablet (iSlate?).
I doubt that simply porting existed OS to a 10” touch screen may take "you-know-who’s considerable undivided attention”. Having an entire event dedicated to the mobile market Apple will most probably try to set a new standard. 3D User Interface may become just the thing to mark a new step in evolution of UX. Apple has been working on various 3D systems for quite some time now: 3D Projection System, 3D Desktop, 3D Displays, etc.