Previous articles make Blue available as an upgrade to valid licenses of Vista, Windows 7, Win8 (maybe XP - can't recall)
In those discussions (rumors?) Blue was seen as a new licensing and distribution model. Annual subscriptions($40?) would replace a packaged OS, more frequent updates (mini-svcpacks) and Win8 was the name that would last.
Most of this is good news, I think. Except for the annual licensing. By the fourth year, I will spend more on the OS than I've ever spent on an OS. Some I still run after 18 years.
I'm not sure how WU plays into the scheme. Perhaps if you do not renew the subsctiption, you will continue getting updates through WU unitl the life cycle expires (same as current support).