Recently, I discovered that patentlyapple.com had acquired what seems to be a patent filed by Apple for an iMac Touch ( Actual name unknown ). Needless to say, if Apple has actually developed it, they are still a long long way from releasing it. However I'll elaborate on what I seem to understand from this design.
Apparently, the key to it all is the base, or as the header of the image says "Flex base". Essentially when the screen is in the upright position as shown in the main center image, it will function as a normal iMac - on Mac OS X ( Or whatever the latest version of Mac is by then ). But when its screen is facing up such as in the figure on the top-left corner of the image, it will function as an iOS Device. Needless to say, this seems like an extremely convenient idea but for the obvious disadvantages such as which keyboard will be used and if its a touch keyboard won't it be extremely inconvenient.
Another appealing possibility, perhaps most likely too, is that Apple will develop an entirely new Operating System meant for such devices.
Of course, there's still a lot of thought that needs to be put into this, but I'm hoping that Apple's already doing that.