Touch screen computers have no use as long as they are mounted VERTICALLY (resulting in a gorilla arm...), but why should Apple not equip their new iMacs with a cool new kind of hinge that allows you to swipe the machine into a stable, HORIZONTAL position. When flipping the machine, it will automatically invoke a kind of TouchFinder (similar to FrontRow), an overlay to the real Finder that has been optimised for touchscreen use (larger buttons, etc.)! Imagine sorting your images in iPhoto touch on that gorgeous 24" screen laying almost flat on your desktop! Imagine cropping a video in iMovie touch! And surfing the internet using Safari touch for the new iMac with onscreen overlay keyboard. And if you want to go back to regular use (egg. to write a paper), you just flip the machine into a vertical position again and you will be back in the regular Finder and are using your keyboard and mouse (that were just hidden by the machine in it's horizontal position).
Now, wouldn't that be genious? Toss in BlueRay and -- boom! A killer machine!!
Genius...in the land of fantasy. What you're talking about would require not only a complete rewrite of the OS, it would also require a complete overhaul of all hardware. Not to mention all the third party stuff which would have to be reconfigured. i.e. completely not something that would come out in September or anytime in the next few years. The problem with touch screen is that although some people and some devices have a use for it (iPhone etc), most people and most desktop devices do not. For Apple the problem is how to incorporate what would essentially be a new UI that is not only practical but universally implementable in the Mac platform. In my opinion they are going the right way about it by doing it via touchpads, not touch screens. The morph from mouse to touchpad is cleaner, easier and more ergonomically logical than that required from mouse/keyboard to touchscreen (not to mention the additional cost of physically producing touchscreens).