We knew this would happen eventually, especially since the name of the Authenticator changed on the PTR from being World of Warcraft specific to a more broad Battle.net name, but the fact that it's coming without formal notice is a bit surprising! If you're unfamiliar with what a Battle.net account actually is, it's more or less the same as your WoW account but instead of an account name, it uses your e-mail address and it spans all Blizzard games. Considering the Starcraft II beta is rumored to be starting quite soon, this is probably good timing for the switch.
We have no idea if this switch is happening in the US yet, but it's probably a safe assumption that it will. Or if it hasn't, we'll be seeing it very soon. If we find out more, we'll be sure to let you know.
Update: It does look like this is coming to the US soon as well.
[Thanks to everyone for the tips, and Kumbol for the screenshot]