I doubt that they will ask for subscription for the OS itself. I think they are more likely to go the iOS/Android route and will try to monetize Windows with the App store introduced in Windows 8.
And of course owning the Desktop OS market continues to put them in a strong position in the profitable enterprise market which doesn't mind paying for features and support.
And of course owning the Desktop OS market continues to put them in a strong position in the profitable enterprise market which doesn't mind paying for features and support.