My bet is if you isolate the VM in Parallels as I do, Cortana won't work. Maybe you are correct and it will but I have my doubts. Not due to how it works but because Parallels won't have an option for it alone. We'll know soon enough I guess.
Just about every older person that was stuck with a PC I know now uses an iPad rather than buying yet another PC due to viruses and malware. This as oppsoed the Mac users who are still upgrading to newer Macs. The profits or lack thereof at MS seem to reflect this trend.