Unless you composed a break-through development of keeping a six pack while in your bulking stages then I'd really like to know that.
The purpose of bulking is to gain good lean mass.. and turn it into muscle.. Meaning you will be gaining weight, but in a good sense.. Your 6 pack will come back once you have finished your bulking stages, and start cutting. I don't see a reason why you would want to keep a 6pack when your bulking? Because a person of your physique will need to gain weight. Thus will hide your 6 pack..