Of course they can. I have no idea what NotTarts is trying to say, but I have embedded products that we run CE, NT and Linux on. Same hardware.
Given the problems with the Mango update (several month delays for some handsets due to technical issues) I wonder if there's some none-obvious technical issue that's deterring MS from a Windows 8 update? It's hard to see the likes of LG and HTC putting significant work into overcoming issues with old handsets. Would it be better or worse to only have selected handsets able to manage the upgrade?