I can't imagine a hinged dual display being "sexy" enough Apple. If you absolutely need a keyboard, get a bluetooth one.
Trick optics or a flexible display might make it sexy enough. "Look, there's no seam!"
But also running with your idea -- what if the unit contains an ultra-thin detachable wireless keyboard, achieving surface-angle diversity even better than a hinge?
Otherwise, it might prove awkward as a remote-getting-stuff-done unit -- in libraries, cafes, airplane seats, etc.: if flat for typing, it's hard to read; if angled for viewing, it's hard to type.
A symmetrical hinged dual touch display, as in the next-gen OLPC2 prototypes, might do the trick. (Could lens/optical tricks make the seam nearly invisible when flat? I wouldn't put it past Apple.)
Here's the OLPC 2.0 dual-touchscreen concept:
http://www.engadget.com/2008/05/27/olpc-xo-2-to-include-mult...
http://www.engadget.com/2009/01/28/olpc-2-0-dual-touchscreen...