It's not quite confirmation of a Bully 2, but this bit from Rockstar's Dan Houser in a Gamasutra interview does give us hope. While responding to a question on why Max Payne 3 is returning now, Houser brings up the Bully franchise.
"We knew that we didn't want to start doing the Bully sequel instantly at that second with those guys -- even though it is a property that, like Max, we adore and might come back to in the future. There was just no impetus to do that then," he said.
"So we said, 'You can do Max, and then we will see what we can do with Bully.' So it was really waiting for the slot to open up and the group to open up to at least start work on it."
Don't go thinking that they'll take up Bully 2 right after work on Max Payne 3 finishes. That would be nice, but it's not likely, especially when you consider how long it took for them to follow up Max Payne 2. At least we know that they're thinking about it.