I have watched a lot of videos in the UK where Shaw Summers, a leading bariatric surgeon, removed gall bladders seemingly as routine during bariatric surgery.
I had mine out separately prior to my bypass and I'd say go for it. Anything that saves an extra surgery down the line is worth it. The gall bladder surgery I had was keyhole and easy to recover from, but one anaesthetic has to be better than two I think. My own opinion only of course.