It does occur to me that potentially the Courier could still be pulled off: get an OEM or two to produce the dual screen hardware (didn't one OEM produce a laptop similar to this last year?), refactor the Courier software experience to Windows 8 and you'd have a pretty good 'premium product' built on top of Windows RT. I'd buy one... I would imagine that the battery life and weight of a dual screen laptop like that would suck though.
Wouldn't be suprised if Microsoft or a.n.other company take some of the courier ideas and principles and produce something nifty for Windows 8 tablets with it, even if it's initially for single screen tablets.
If not - Microsoft should release the software as an open source developer challenge - get some interest around the community in taking it and getting WinRT developers to do something cool with it - never going to happen though....
Courier wouldn't work well with the in-box Immersive UI you see in Windows 8. What they would need to do is add features to Windows 8 which would allow it to function differently with two or more screens --- whether it be on a dual screen device like the Courier, or with two full desktop screens. "Courier mode."