That's exactly it - I don't think the userbase cares. (Hell, I think to much of their userbase, "Windows" is as much of a liability as it is an asset.)
That tying-stuff-together mentality is something that has served Microsoft well while they've dominated, but is increasingly a weight around their necks as areas become important that they can't extend domination into.
Since word on it is getting out to a group that needs hyping, it might be a good idea to have started openly calling it "8", then. Build some excitement.
Guess they've got the idea that users associate Windows for PCs 7 with Windows Phone 7 which seems to me ought to only be a minor consideration.