My philosophy is that you don't pick a goal weight -- your goal weight picks you. That probably sounds silly, and it's sort of an exaggeration, but when you're talking about the massive weight loss one gets from weight loss surgery, it's not necessarily practical to target a specific number on the scale. I didn't really have a "goal weight" -- nor did my surgeon -- until I went to my psychological evaluation and the psychiatrist asked me. Even that, I think, was mainly about checking to make sure I had realistic expectations. The number I gave was based on the average/typical weight loss for gastric bypass patients. I think I went with 180 pounds, but I actually ended up around 140.
To me, the number on the scale is pretty meaningless. And I say that as someone with an analytical mind, who loves numbers and spreadsheets and graphs. The non-scale victories are far, far more important to your quality of life. First, and foremost are the health goals -- things like getting off of medications, having a healthy blood pressure and blood glucose, etc. Then there are the physical benefits like being able to walk a mile without sweating or a few flights of stairs without getting winded, and not having constant pain in your feet and knees. And of course the social benefits of literally fitting into the world -- flying without a seatbelt extension, sitting in a booth at a restaurant, not having to worry about weight limits on furniture. Finally, being more confident and satisfied with your body/appearance, having more clothing options, and being more accepted by people and society in general (which is really sad, but true).
I think if you are fixated on a specific number on the scale, you can lose sight of those important non-scale victories. I'm not saying you shouldn't track your weight (I weigh myself probably more than I should, multiple times per day) or that the scale isn't important to your progress, but you don't know what the number will be when you hit the point that you have lost enough weight to improve your life. That's especially true when you start out at a high weight, because your body will not be the same at 220 pounds (after losing 200+ pounds) as someone who has never been higher than 220 pounds, because your body will have more skin and bigger bones even with the same amount of fat and muscle.