I think that you need to get to your goal weight and see what is available. Having the BBL performed and then losing weight may cause the fat to shrink in the buttocks as well.
Enough fat for revision BBL?
Hard to know how much fat you will have left after your additional weight loss. That being said, if you have a fat transfer and then lose a bunch of weight, most of what you'll lose will be from your butt.
My best advice is this - achieve your goal weight first and then seek consultation. You may qualify for BBL, or you may need implants with or without BBL. As long as you are at a weight that you're comfortable with, we don't have to worry about you losing all your transferred fat.