Gonna give my two cents here.
They haven't announced or revealed a sequel to Bully, yet, because they still have a bunch of other games on their back right now. Seeing how this thread was created after L.A. Noire was released, they still have Grand Theft Auto V, Agent, and Max Payne 3 to come out. They probably are working on a Bully 2, or at least in pre-development stages, but they're not gonna announce in the middle of marketing other games that still have left to be marketed.
GTAV, suggests a 2012 release with Agent probably coming the same year or the year after. I'm not sure about Max Payne 3; perhaps at the end of this year, or next year also.
But on or after 2012, when all the hype of those games are disappearing, I'm sure they'll announce a whole new set of games. Uptop claims Rockstar New England's working on something "awesome", whether this is Bully 2 or something else, I don't know what else it could be. Rockstar Leeds got their Vita game, and I'm not sure what else in store for other Rockstar studios.
All I'm saying is; don't lose hope, but don't expect it anytime soon, either.
