I don't know how Metro IE and Desktop IE are separate or one and the same, but from what I read, only Metro IE would be available to some devices, most notably ARM tablets.
AFAIK, Metro is always available, but desktop IE is only available on x86 (or the like).
That hasn't been confirmed and probably isn't true. John Gruber came up with that theory based on what he felt were hints from Microsoft but that seems to be dis-proven by this ARM tablet running Windows Desktop: http://thisismynext.com/2011/09/14/nvidia-kal-el-windows-8-t...