Of course you never know, but
usually the first time any dates for the next year (in this case 2013) will be seen is when the BB changes (
usually sometime in August) to a FD BB that allows you to book a package a year ahead for the next years FD dates. Then after that BB FD package expires (
usually sometime in Oct/Nov) there
usually is a room only BB that starts that includes next years dates.
So to sum all those "usually's" up

- sorry, but you probably won't see any 2013 BB dates when you go in March/April. But you never know with Disney! They could change it all around this year!
Good luck!