Not only that, OS X doesn't run on ARM chips, and never will, or it will cause confusion with people when their app runs on their Mac but not on their big-ass iPad not realizing the CPU architecture is totally different and totally not compatible.
A couple of points here.
iOS
is OS X. With darwin, CoreServices, CoreFoundation and Foundation, the
only significant differences are a handful of classes within AppKit, which very, very easily could be added in to iOS-Pro.
And as to the difference in CPU architecture, Apple has made that all but irrelevant, at least for modern apps. All developers are now expect to deliver apps in what is called "LLVM Intermediate Format", which makes them architecture-agnostic.
So, yeah, a decent OS X, adapted/enhanced properly for touch UI, is entirely possible and not a huge jump from where we are.