If Apple did bring out a touch screen equivalent of the iMac, then I don't think they'd market it as an 'iMac' at all if you see what I mean. It would probably have a different form factor to make it useful (ie horizontal) and as such wouldn't be an iMac as we presently know it. I'm not saying that such a thing won't happen at some point in the future, I just think it that if it does it will represent a new category of Mac althogether.