Originally Posted by solipsism
If you an entirely different UI with a completely different set of drivers, varying frameworks and foundations that arent needed from another device then its not a different flavour OS. By the reckoning that the core is the same then AppleTV OS, Mac OS and iPhone are the same OS because they use Darwin and certain fall under the OS X umbrella. My money is on this being a bulkier OS than iPhone OS and having a distinct name.
PS: I have to assume that with the emergence of the iPhone OS being so lightweight that the next AppleTV OS will be based on it, rather than Mac OS X.
AppleTV was basically a slightly altered Mac OS X 10.4. I'd class it as the same OS.
iPhone OS made significant changes to most frameworks. Not much, but enough. Foundation, for example, was cut down dramatically in size. Many layers of the OS were optimized for mobile usage etc.
The definition of an OS is difficult to pin down. I'm on the fence as to how they will advertise this to developers. Perhaps they will ADD to UIKit additions for tablet-only use. Maybe an additional kit and the tablet also running windowed iPhone apps like widgets.
But there's one thing I'm certain on: if they're going to use a platform, it would be iPhone OS. iPhone OS is not, in itself, limited to the look, feel, access and capabilities it has ATM. That's Apple's choice in how they've developed UIKit. The OS core (and the changes from Desktop OS X) are just as capable as the mac version.
UIKit, however, is currently not up to that same complexity and heft.
Perhaps changes to the UIKit, perhaps adding a new framework. Maybe both. But will it use Desktop OS X? No. Desktop OS X is just the same, plus a tonne of backwards compatibility, flash, and other dependencies that are simply unimportant for a new touch device.
If they'll make a new mobile device, it will be on a foundation of iPhone. Not a foundation of OS X Desktop.