There’s been a lot of discussion in recent months about the likelihood (or not) of Apple releasing some sort of tablet computer. Some people think Apple should; others are convinced that Apple never will. After Tuesday’s keynote, I think we will see a Mac tablet of some sort or another. Let me explain why.

The key is Multi-touch. This technology is simply too good to simply be a UI trick for cell phones. Imagine being able to shift your files around in the Finder by touching and “flicking” them to different locations. Think how you could edit photos if you could use your fingertips to zoom in, touch up, move sliders around.

Multi-touch is just begging to be used on larger devices. Maybe not on any of the notebooks we already see, since they are already quite large to be held in one hand, and you need to have one hand free to perform the touch gestures.

Just as the iPhone will be a premium cellphone product, appealing to a minority of users with expensive tastes and budgets to match, I don’t see why a larger device - somewhere between the form factors of iPhone and MacBook - couldn’t be marketed as a premium notebook computer for certain kinds of computer professionals. Public speakers. Photographers. Journalists. It might be a very small notebook; perhaps they’ll call it a large iPod. Whatever they call it, in my mind, Multi-touch has an obvious evolution path in that direction.

I think Multi-touch is the most exciting thing about the iPhone, and it has a key part to play in the future of Apple Inc hardware, be it computer or consumer device.