I suspect, and there have been various MS comments to suggest it might happen, that there will eventually be a WinRT target for desktop (non-Metro) applications.  That pretty much has to happen or WinRT will be largely a wasted effort.  I think MS isn't saying anything about it now because it hasn't been worked on at all yet (all resources have gone into the Metro support).  WinRT will get beefed up to be a more complete framework for both desktop and Metro targets.  At least I hope so.  The disappointing thing is that MS won't describe what is planned.  They  are trying to force developer attention to Metro apps while ignoring the elephant in the room.

My company is just beginning to move partially away from XP and onto Vista (yes, I said Vista, not Win7).  It will be another 10 years or more before something other than traditional desktop apps are even an option.  MS's current direction to continue building native GUIs in MFC or pure win32 just isn't going to cut it.