Coming from a Gamasutra interview with Rockstar's Dan Houser...

GS: Can you discuss the catalyst that made you decide its time to bring Max back and do more with him?

DH: Basically we have been meaning to start it for a while, but we have limited bandwidth and limited studios, and more games to make than we've started. So suddenly it was a good slot.

Also, contrary to a lot of people, we like to take a little bit of time at the end of a game before starting a sequel, so we can wait for the excitement or disappointment and everything else of the experience to shake down and really see what we should do in the next game.

So 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.

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.